Yes, I'm imagining how easy a job it would be if YOU do it! 
Seriously though, like your lighting board, this would be a contribution to the hobby.
When you open up the 4-channel system, you will find a custom chip that has address pins so that you can control more than just 4 channels. I'd think you'd want something like that (say, at least 64 total devices, 4 at a time, by setting some programming jumpers or whatever). The protocol is very simple as you can get the datasheet for these RC chip pairs on the web.
As you correctly point out, part of the issue with all this RC stuff is dealing with the momentary vs. latching vs. toggling issues. So in the case of the ASC/SC2/AIU devices that close an SPDT relay, you have to burst out the RC signal rather than leave it on continuously. So if you have a loco trying to transmit to a caboose for direction lighting, if you hang the transmitter on the reverse light in the loco/tender, you only want to send a short burst 1/10th second burst on each direction change rather than spraying continuous RF when in reverse. Obviously that kind of edge logic, timing, serializing of the protocol is child's play for a 50 cent microcontroller chip.
I don't believe there's any economical/practical solution to remote-control of rolling-stock in O-gauge.
