So I was browsing that there Kickstarter and came across the WiPhone and saw how they are doing the case design is very interesting:
The back is a blank PCB, but you can replace it with whatever you want with pogo pins on the back.
I am extremely interested in something like this for the future. Pogo pins are overkill, just copper fingers should be just fine. Also Arduboy would is much more thin. Would actually probably be looking at intentionally leaving a bit of negative space on the inside so chips could be installed.
Maybe the new Arduboy platform could just be the buttons and screen and it’s up to you to chose what motherboard you put in it.
Edit: The more I think about it, that would be pretty cool as the 32u4 would work very well as a GPIO processor and also a usb to serial bridge for a bigger chip.