I edited my post to say "more like" a DX7. Unfortunately velocity sensitivity can't be added because the physical keyboard doesn't support it. The firmware does add velocity sensitivity to incoming MIDI data though!
I wonder if it would be simple ot add a sensor to measure that across the keyboard, and then have it do double duty as aftertouch (aftertouch is an effect that measures if you "wiggle" a key after you've pressed it down) Then his DX9 could be better than the DX7 :)