Re: BP Signature Profile plugin
One way of doing this is to create a new textarea profile field entitled “Signature” and call it within each BP component you want to use it in.
I know one of the BP mods, John James Jacoby, does this for one of his BP sites, specifically the bbPress forums (eg. a forum thread – http://delsolownersclub.com/discussions/topic/what-will-your-next-mugen-part-be), but I believe he only uses it for the bbPress forums and nowhere else across that BP site.
However, I don’t think it would be *too* hard to call it within the group forums and the wire (I say *too* hard with a little skeptism! hehe). You just would need to edit your BP theme in a number of places to do so.