Hi westfw, thanks for your suggestion.
I actually thought about that as a possibility.. It could work, I should do some designs as tests to check for it's feasibility..
Anyway, I don't think that breadboard compatibility is actually important as I imagine this board to be used in very specific applications. Eg, It could be a good thing to have for people already having PCB designing experience and they could just as a building block in size constrained applications when they would need to add Arduino intelligence to their designs..