I don't see the need to modify the forum code for this. There's software for virtually every OS out there to provide keyboard macros. You define some key combinations, like CTRL-B or maybe Shift-CTRL-B for bold, and this inserts [b]|[/b] with the cursor | sitting between the BBcode tags.

I guess, more sophisticated software could allow the distinction to wrap selected text with the appropriate BBcode tags or if no text is selected, insert the tags with the cursor sitting within the those.

I mean, I wouldn't mind if the post entry screen would recognize certain key combos by the underlying forum code, but you can have basically the same with some software addon.