Why not a small foot controller and some extra 'dumb extension boards' that can be hooked to the main controller?
Different designs of these 'dumb extension boards' could then be developed with different combinations of extra switches, feedback (LED's, display,..), expression pedals, ... while the main controller stays the same.
This would make the controller more expandible and therefore more easy to upgrade.
+1 It would be a cool feature to have a basic footcontroller which could be upgraded with different attachments (with or without pedals...)