Hello all, i just registered to this forum.
For a while now i am thinking about a design for my midibox that i am
going to use with FLStudio's mixer, i want to use
- one 8x8 monome keypad for the routing from channel to channel
- two 8x4 monome keypads for channel control (together with 2 rotary
encoders)
- three scrub wheels (two for scrolling through mixer channels on x and
y axis and one for scrolling through FLStudio's playlist)
- one LCD screen
- play,pause and record buttons

I will post a 3d model i made of this idea as soon as i get home.

My main concern is, will it be hard to design the 8x4 keypad PCB's?

boardfiles are here:

http://monome.org/40h/kit

at the bottom. so no, it will not be hard. just delete half the board.

That's nice, just like i hoped!
What do you think is most easy (for the board design) to add RGB leds? 
Create a new board layout or just add a few extra wires for every RGB 
led?

I'm working on a solution to control 128 RGB leds so if i manage to get 
this to work i will implement it in my midibox/monome

i'd probably start a new layout, based on the old one.