It could be done manually, but this is painstakingly slow, and painful.

I was looking for a "MIDI Compressor".

I thought it would be simple to have an algorithm that works similar to the way an Audio Compressor works. The algorithm has thresholds and applies intelligent dynamic adjustment to values based on the note velocity information.

Fellow forum member rockstar_not made this useful comment:
Go to platinumears.com and grab the velocity curve plugin. You can draw in a compression like input output curve with it. I had to do this because I didn't like the limited velocity curves in my Casio XW P1 when outputting to some piano VSTi.

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