I haven’t implemented my PicaXe IR Crumb yet, but I propose to set 3 parameters in the picaxe. These can be sent to the crumble as 3 pulses, the voltage of which convey the parameter value, and the duration can indicate which parameter is being sent. I think 20 distinct voltages can be used, and 3 distinct durations.
All 3 parameters can be sent at start-up (from EEPROM stored in the picaxe, and individual changes sent with a single pulse.
It does mean the crumble code must scan the input continually however.