Well, there are plenty of 3-rail electronics guys here, I'm just one of the pack. 
As for the K-Line Cruise board, there is no way I know to "cheat" it and make it function stand-alone. That being said, there is a conventional version of the K-Line Cruise board that does run stand-alone. It also looks exactly like the command version, but I'm assuming it has different firmware. Since we don't have the firmware, and no way to get it, it's not possible to make the command version into the conventional version. I actually have the tools to load firmware on those boards, but no source for the actual code.
As for a comprehensive source of 3-rail electronics types, don't you just wish such a thing existed! 
In our dreams it would also include complete schematics for each type. 
Well... no, such a source doesn't exist. 
I see conventional boards coming around all the time, and from time to time I have sold of excess boards that I have from command upgrades.
As for conventional vs command, both are certainly viable ways to run your RR. I personally like the command environment, and the ability to run multiple trains on one track, the pinpoint control, and the great sounds keep me in the command camp.
