FWIW, I hunted around a bit 6-8 months ago in hopes of finding a similar solution for a friend (use an IR JP1 remote for an RF-only satellite receiver). I looked on Smarthome and Googled the various comp.home.automation and rec.sat.tv.whatever newsgroups, but didn't find anything that sounded like what I was looking for. Most of the IR-to-RF stuff is simply for IR range extension.

It's a longshot, but you might try searching the Yahoo archive of the JP1 group. Occasional wierd OT stuff flies through there.