WYSIWYG I've recommended TinyMCE (its license would allow it to be combined with little issue, other than setting what BBCode we actually use and all that good stuff)
Search able member list I believe is on the docket, right after a js library is agreed on...
I like your search suggestions
...
I am however curious how "An optional confirmation screen displaying similar threads by keywords before a user creates a new thread. This would prevent duplicate threads." will work; could you please elaborate?