Well, I'm still thinking about this, as I really dislike users that quote last post (and first post completely, especially very big posts).
If it is possible to affect how quote button works, to check if it is actually last post in a thread, and if it is, not to quote, if it is not, to quote.
So, all buttons are left in their places, but there's a check of posts position and quoting content, or skipping quoting altogether.
I guess this is a bit tricky, maybe even not possible.