I'm no developer, for sure, so I could be wrong and often am. I believe you are correct in that AOSP Roms have to have a built from scratch RIL for the reason you gave. I am also of the belief that when HTC gives up the source code, we (the developers) can complete the RIL so that it is as fully-functioning as the Sense ROMs. The problem right now, as I understand it, is mainly getting 4G to play ball right, it kind of messes everything up. I didn't get my Incredible until late in the game, but I have the impression that there wasn't such an issue getting data to work with it, at least not for the same reasons. But again, I could be wrong.