Analogue-sequencer

I was reading through some posts here on the forum regarding extra
control over the P3 without using menu pages and there were some
suggestions about a P3 MKII or even a P4, with an altered user
interface with more dedicated control.
Does it make sense to suggest that maybe a 'control box' could be
built to sit alongside the P3 with some dedicated pots and switches ? 
This could be done over MIDI or via an extra dedicated I/O board ? 

(cfr. a modded TR-808 I saw with an extra control box with about 8
pots to control extra parameters, and there are other examples, like
the first project by Access, for controlling a Waldorf if I'm not
mistaken)

I haven't read the manual in detail yet, but if some parameters can be
accessed via MIDI, then a normal MIDI box would be a start...

Off course, if this couldn't be done, and a P4 would be designed, I'd
buy one for sure, because I had so much fun building the P3