I guess that would be easy enough for the simple HTML tags, but vB Code mostly suffices for that. It's the more complex commands that you seem to be looking for, and I guess that would require quite a bit of work (e.g. this page on ampersand-type commands).
Anything other than ampersand commands could be added to the vB Code by an admin. I think it's quite easy to add that sort of thing from what I remember.
