Key-Specific Analog Modifier

[Jimothy]

I play SSBM with keyboard.

*copious amounts of sad trombone music*

I have finally mastered the art of the wavedash, and am looking to now control my w.d. distances.

Is there a way to:
a) make a modifier key apply only to certain inputs?
b) connect multiple keys to one control, and designate a different analog range to each key?
c) do something creative with Dolphin that I haven't listed?
d) use a different program that does something that might help?

Any input you can give me would be much appreciated, and any non-"give up, it's impossible" input would be even more so!

Thanks!