That's an interesting thought Stan, that shouldn't be that difficult. I was thinking of creating a TMCC serial stream processing board so that I could trigger stuff from the remote. Obviously, that's more work, but I want to develop that for other projects as well.
I'll have to think about the board you suggested, I haven't taken one of the remotes apart to see how it functions. I suspect that you could use the internal remote board and just trigger the button inputs with the relays of the ASC or AIU directly, all you need is the interconnection board. You can program either for momentary or on/off, seems like it covers a lot of ground. That actually sounds very easy! 
The custom board would basically be an interconnect board. I suspect many folks would like it if it came all assembled with the remote board as a package so it was Plug-n-Play.
The 99 cent board you show needs to be modulated, so the processor would probably be used. If you just put a logic level into the input, it only triggers briefly. I don't see why there would be FCC issues as the modules are doing all the emitting, and they're being sold here. I have a couple of those sets, and I was going to use one for my Aerotrain to put a reverse light in the observation car controlled from the locomotive. I don't want to run a tether through seven cars to get the job done!
I think I'll take a closer look at the 4-channel remote, that's actually a very attractive idea to get something up and running pretty quickly. I have a few SC2's in the closet, as well as a couple of ASC's. I do have a couple of AIU's as well, so I have all the environments to test with. 
