Button to press keys

With the program mentioned by ozxar you can create an executable macro. And then you can simply add a shortcut to that macro to your True Launch Bar. There you have it: a TLB button that simulates a keystroke (or even a sequence of keystrokes).

It'd be a terrible job to rewrite everything as a plugin, and even a waste of time and effort if an excellent external program already exists...

Part of the fun is to investigate how to add functionality to TLB by using (or exploiting) these existing programs... Just give it a try