I've wanted to add 3 pedals to my digi Ps.
My Casio Privia 88 key digi piano is capable but requires a special plug. You can buy a pedal for it from Casio.
My Yamaha 88 keyboard will only work with 2 pedals.
Most of my virtual instrument pianos will use 3 controllers.
I've thought about adding a MIDI solutions F8 general purpose input to MIDI for the Yamaha.
The bottleneck is the keyboard, and the type of connector it uses.
I recommend you determine what will work with your choice of keyboard and go from there.