Wow, spk77, I looked at the code... Way too deep for me...
I guess for staccato/legato I would imagine the top line setting length of note, and the bottom setting the peak or dip in the curve of contrast.
For accelerando, I dunno... Would only 2 adjustments be required? Moving the curve/sharpening it toward the end on one line (constant vs ???). Determining which end is faster/slower and by what magnitude with the other (difference)? I guess start position would be the base? Maybe you can see a good way to work an acceleration formula in to your device? Me bad at maths.
I may be looking at this all wrong.
I guess I should just mess with the velocity/cc device for a while, hey? Just figured if it is easy for you, you could slap something together. If it's a lot of work, I don't know if anyone else is even interested.