I will need maybe help with board, because I'm never doing that (at least not the ones I finished 
) So, every suggestion will be useful.
Idea for button is that only 1 button (for brightness) will be soldered on board, which will be coming out of the case. It must be close to the case.
Main ON/OFF button will be attached on case.
For Digispark case will have outside hole for USB.
For scheme, the most of the wire can 'hanging'.