I guess you may have the wrong idea, here. Let users create their wallet with any identifier they want (some of them may already have one) and you’ll ask them to fill their identifier on your forum. This seems easier and more logical.
Then, you have to think about one thing: Is it better to do a transaction for each “tip”, or to collect all the tips in an internal account for each user, and let them withdraw when they want to (or on a scheduled basis, like end of each month for example). Are there fees on transactions ? Does it make sense to have a lot of very small transactions ? (I don’t know right now, but fees were quite high on Bitcoins recently). It would seem to make more sense to me to collect the tips and work with withdrawals. Sure, users just have to trust you to keep the amounts until they withdraw. You can keep this in a centralized crypto account where it is visible it’s parked there in the meantime.
If you work with withdrawals, there is even a pretty simple way to it, and not requite any “linking” or integration at all. Users can use any wallet they may want, and they just have to enter the address where they want to receive when withdrawing.
Another thing to think about: Do you want to use likes ? That already exists, you just have to track them. Or you want the plugin to add a separate “tip” button ?
Just decide about the above points, and the principle of the plugin doesn’t seem excessively complicated. I can put into clear words for you if you want, and you’ll just have to find someone to actually code it.
Note: You could always have a button to trigger the generation of a new wallet with the service you have in mind for people who don’t have one, and want to use this. Provided the service can be called to do this and you can get feedback in return like you’re describing it. Or you tell the users to do it there and just enter the identifier on your forum afterwards.