This is an interesting issue that I have faced too. I am not sure about the idea of the “Second Post Wiki” being the solution however.
The issue I have, which I presume is the same for you, is where a user creates a New Topic with a long, interesting and varied post. The answer to this MIGHT be to create a wiki post, but the admin (or person suggesting this solution) isn’t always the first to reply.
It means that the original post either needs to be completely re-written to present the issue and store the ‘wiki’ information, or a whole new thread needs to be started. Without asking a member to do a lot of work, Admins are required to write the post as a reply, add the initial content, move this to a new thread and then re-assign the post to the original member (who may not understand how the admins have posted on their behalf).
Would it not be easier to re-organise some threads so that any post in a thread (particularly for wikis) could be made to “jump to top”. I realise that this messes with the clean post-in-order format, but it isn’t hugely different to showing the content of a reply or in response to post out of order.
“Jump to top” could also be useful in the case of new threads being started by moving an existing post into a new thread. Unfortunately some “off-topic” replies that need to be moved are sometimes worth keeping, but do not make sense as the first post of a new thread without context. It would be good to be able to write a brief “this is the issue” post that could then be made to appear at the top for new readers.