There's no reason why the four commands couldn't be used in combination:
cmd1, cmd2, pause, cmd1, cmd2 ...
giving 16 possible combinations, or 64 etc.
Might be game pieces telling the robot what state they are in.
"Busy", "Ready", "You Scored", "Go Away", "Red Team goal", "Blue Team goal ", "Penalty for using", "Extra Points Now!".... endless possibilities.
I wonder how many games we could come up with that are not the one for FRC 2008.
Possibilities increase if the robots can also send commands.
Remember - it's all idle speculation - we just don't have enough info.
As for the interference - mount the receiver in a box and make it look down a tube, it'll become very sensitive to direction and less able to be interfered by another transmitter.