This is what I did to add a better hmtl editor, at least for IE (the author is working on a mozilla compatible version):
http://pafayo.neza.net/nukes/howto-add-htmled.html
Great work.
I configured PhpBB 2 with WYSIWYG, but it is buggy and not working although PhpNuke works with WYSIWYG.
I would really like JBoss-Nuke-BB would include the WYSIWYG very soon.