It's probably not the answer you want to hear... but I totally know of a way to do exactly what you want. Install and run Penquinbait's KDE as your desktop environment instead of Maemo. I've been using it since Xmas and love it. It is a little slower than Maemo but the gained functionality is more than worth the few seconds.

I've got keyboard shortcuts & hotkeys mapped to launch favorite apps, to control XMMS while it's playing in the background and I'm in another app, I've remapped most all of the the hardware buttons to match my personal usage.

Another alternative is you use xmodmap to remap some of your buttons but I don't think it will allow you to launch apps and such.