So, the key here is that you'd prefer one bank of buttons that stay constant, along with another bank of buttons that are switchable. Hmm.

I would have guessed that it would be easier to, say, map the arrow keys onto some of the lower buttons on the remote, rather than overload those five buttons near the top. Are you using those five keys for Eventghost because you aren't using them for your other devices?

I thoroughly concur with this sentiment! I've gotta say, though, that this is exactly how Pierogi came into existence.

There has been a lot of talk in the past about creating alternative front-ends to Pierogi, and I would certainly like to see that happen, but I've never managed to really clean up the back-end enough yet to make it available as a separate library. Another project I really need to get done someday...

Yes, I absolutely support the idea. The Pierogi back-end, even if I manage to turn it into a library, might still be a little heavyweight for your immediate needs, though. You might try starting out with a straight-up front end to the LIRC server; several other remote control apps work that way. But yeah, the most popular languages for coding on the N900 appear to be C/C++ and Python, so that's something you might want to check into as well.