MyBB Hacks

Obviously only certain special members should be able to use it.

I am looking for a plugin that lets you post as any user without having to log in as that user.

The "change user" button just logs me out.

I haven't heard of any such plugin.
Probably not too difficult to write up, so you could try asking someone to do it though.

You just modify the insert query and the post form to include a user id and a user name.  Then if you can't mod the mod panel, you make some if statement to control who gets that.

If i had all day, I probably could write it, but I'm too busy.

So I guess I'll ask.  If you can write it, go ahead.