I would pay money for a 76 note PSR2100.

A 76 note PS2100 with an extra RH keyboard zone would see me reaching for my wallet without consulting the wife!

Aftertouch is a nice thought but unchievable without a redesign that would involved replacing the entire keyboard mech with something of PSR9000proTyros standard and I don't see that happening except maybe to the Tyros that is.. an 88 note Tyros would be interesting but I think the price tag would be very serious.