At the moment you have a possibility to define fixed step, you immediately hit a plug-in/parameter which has not uniform fixed values (at least I had such experience
).
The only universal solution I have in my head is a map for all parameters (REAPER and FX) which defines:
* parameter type: "continuous" or "set" (subtype for "set" is boolean switch)
* for continuous: native step size
* for a set: exact fixed values
Also per device there can be coarse and fine step sizes plus the number of ticks per switch for a set. Step sizes required to adjust the speed of encoders (the range of ticks per elevation is to wide to be universal) and ticks per switch are required for relatively buggy encoders which can trigger more then a tick per movement.