I see there is no voting on membership to core by all the users. That’s what was being proposed. I have a small, closed community - people from all over the world - but if someone invites another, that person is not “voted in”, they are just in. All of our members are trusted and their opinions as to inviting a new person to join are respected. My only reservation about how this voting by the entire membership thing is you could end up having a clique or two. Everyone is an individual and everything they say may not be to everyone’s liking, but their opinions are listened to and tolerated - unless they go overboard.
Tobias, I see your “core committee” as what others would call “staff.” That is different than having the entire core community vote someone into their ranks. But looking at the OP, @Raj_Rathore says he has must approve users enabled and that’s it’s working, but takes too much time to review. Raj, do you have any mods and/or other staff that reviews new users? And being a closed community, how many new users do you get a week, or a month, that makes it so time consuming to review them? I just want to understand your situation a little more.
Most important, how much of a new user’s info would all the users get to make their determination as to whether they approve a new user?
Anyway, I’m glad you like Discourse and its many features. Hope you can figure out how to make your case usage work for you. Good luck. 
Interesting idea!
Have to agree with @itsbhanusharma. This is so far a departure from core Discourse, this is best implemented as a plugin. Sure that adds to maintenance but that’s rather the nature of the beast. The plugin option allows you to take your own path and not have to convince the main platform to implement your special case.
You are then more the master of your own community’s destiny and can experiment with the regime and report findings back here?
(It’s also a great and motivating excuse to build a new skillset)
Couldn’t you create a group “xyz forum members”, with everything only accessible to this group ? (Or maybe Trust Level could be used to achieve this ? I’m not sure). You then drop the must approve users but only let non-members of the group access one or two categories where how your community is working is explained and where they can describe themselves in a new topic with a poll. Once the poll ran for a certain amount of time, or the results are more than x% of favorable votes when they have at least x votes, or any other criteria, you just have to add the user to the group. That the only manual operation you would have to do. You solely decide to add to the group, but by respecting the results of the votes. Thus you keep a veto right at that point. That part could eventually be automated (the adding to the group, or granting of TL, depending of the results of the poll) but it doesn’t seem very time consuming even if you keep it manual.
Couldn’t it work pretty easily like that ?
The idea seems very neat, but as @itsbhanusharma said, its a bit too complex to be in “vanilla” discourse.
I have indeed created a private membership group and there’s already a feature provided by discourse where a user can request access to a private group and which in turn on that basis grants access to private categories of the forum. But the issue here is that this membership request can be approved by any staff or owner of the group. Let’s say a user requests access, says that he has exposure to certain discipline and is an expert at it and want to contribute in this way and would love to be part of the strategic core committee of the forum and let’s assume it’s a forum for a political party… he mentions and provides some details which can be fake just to gain access and information may get leaked. A Staff or several of the staff may not be able to verify the information or vouch for the applicant. And individual opinion or invitation by one person allowing access in a way jeopardize the trust of other members. Let’s say a politician gets access to the party on the basis of some link at a high level and that person invites and makes him a member of the party… but the fact is other members of the forum may feel strongly against the person as some or many of the user may have known more about the person than even a staff user knows. I hope I’m making some sense. And that’s what I mentioned by another analogy here.
And what I am asking is can be summarized as this that my forum doesn’t have more staff users and staff users aren’t expert at selecting or even rejecting the users, they may know how the forum functions and some of the technical sides of it but not the human perspective of things. And I am a staff/admin at it. I really don’t know if I accept a particular candidate or not. And the community I believe is more an expert at a particular field of interest than I am. Let’s say I create a forum about history or science. Let’s say I create a forum for a scientific community accepting the physicists, I am a programmer and I have links with some of the Ph.D. scholars from college days and so I oblige and create the forum. But I know nothing much about physics, except I had a paper of quantum mechanics and studied some Fermi-Dirac statistics and Fourier transformations and some buzz words like Schrodinger equations and plank constant… and some comparison to classical physics and how quantum mechanics is related to small particles like electrons, etc and some of the same terminology. But I am in no way an expert or nowhere even close to claiming myself an expert at it on the basis just a paper which had and having passed I never looked up again. Let’s say a person has a physics degree but is a renowned lunatic or self-proclaimed expert that the community feels strongly against and I have no idea who is what and known for what. I am in no position to deny or accept the request. And If I induct some of my friends who I think are expert at the subject and make them a staff, then I guess I am wrong in doing that as well, because there’s a bias. My friends are the best physicists obviously… or best doctors or experts because clearly being my friend is the best qualification. So in a way, you can say that I need at least some opinion of others in this process.
Sorry, If I am not able to make my point across clearly. I think I have introduced too many analogies and these may be out of the scope of the subject here… and I am able to give such comparison is only because discourse is really such a fine software and already provides a lot of features that a user can easily get by with provided functionality and even exceptional use cases if you look for. The only point is If my idea is good and if the discourse community happens to value it and like it and it benefits the discourse in some way then it would be great. If it doesn’t then it’s fine as well. Sometimes, you think that something makes sense on the basis of ideology and doesn’t work out in practice. In my case I am creating a community where I don’t know much about the subject at hand, however the community collectively knows much more than I could ever know.
I don’t see any issue.
YOU create the group and are the owner of it.
You and the staff approve new members into the group, by respecting the results of the votes to a poll for each new member (ideally, that each one creates himself).
You indeed do the validation. But you don’t really decide anything. You just do as the votes told you.
Yes, this can work actually. If a member applying for the access to the private group create a topic containing a poll where existing members can vote and they in their request to the group share the url of the post they created about approval. On the base of vote we select the user. This can definitely work 
however, I guess the user creating the poll will know the results and be aware of who voted against him or in favour.
He will know the results in any case (because he will see if he’s entering the group or not).
Can’t the votes be NOT visible by other members ? (I mean the individual votes, the details)
You are also complicating a little the matter for nothing: All new members have to do when arriving to your forum is create a topic containing a poll in a PUBLIC category. Then they can describe themselves there. And others can ask questions if needed.
All you have to do is review regularly this category and add manually to the group people who had favorable votes according to the fixed criteria.
That’s it. Simple (unless I’m missing something)
The individual voting details are not visible by default unless you explicitly check to show the details. Poll creator knows the details though. However, If on receiving the request, the owner creates a topic in the private category and takes a poll and then decide… the result would be visible to poll creator only. This is similar to what I have mentioned in this topic’s first post…
but it’s not automated. It requires the involvement of the staff in creating post for each individual asking for approval. So far, I am approving users based on my judgment. And in cases where I’m confused, I either ask the person in the community who I think would be best suited to give an opinion or sometimes create a poll if more opinions needed or when I am not sure who to ask.
As posted just above while you were typing: No requests. Let users create the polls themselves (in the public part of the forum). It’s then kind of automated (for you). You may just have to adjust Trust Levels to be able to create a poll (as you want very new members to be able to do it).
The creation of the topic with the poll in the adequate category is the “request”.
If that’s really a problem, you may have to find a workaround for this part.
Or finance the creation of a plugin which creates a poll for each request, or new member, in a private category if you want (that would mainly be just to maintain the anonymity of the vote results, or a plugin that does it a different way)
First I’ll go with my manual solution and see the response of the community. If it works really well. I may attempt to create the plugin myself.
Create a route to registration-reviews, notify all existing users having a TL2, by showing a notification in the review section.
Create a setting asking for the closing period of review-poll.
Existing Users will go to the review screen.
They will assess the info and vote for acceptance or denial.
If a specified time passes, the poll will be closed. Users will be accepted in the forum or denied. The poll details will be deleted. The new user will be informed that they were selected or rejected by the community to be a member of this forum.
Another thing to check out is the discussion on Meta around an automatic election system for Trust Level 4. When should automatic leader promotions be out?
The system hasn’t been implemented because it both conflicts with the existing moderation style of many large forums, and is wholly overkill for small forums. … So who’s left to use it?
Experiments are welcome, of course.
I think an election style implementation (probably using a plugin) can be very lucrative.
A simple election system using the votes plugin if it allows voting on user profile
or using polls if the poll results can be assigned to user profile
I’d assume both of those fall under custom plugin criteria
And once the staff decides to declare result, The winner(s) are auto promoted to TL4.