First of all I'm glad you guys like the idea
About the open source thing, yes I intend to go open source.
This will be my first open source project so I could use some advice. I'm thinking of putting it on github under something like a CC-BY-SA licence
CAN bus would be nice, but as far as I can tell (maybe I missed something) the STM32F411 doesn't have it.
The board as it stands is 17x32mm, can be a bit less if I trim it down a little bit, pins are on a 12x6 100mil spaced grid. Maybe I could add a little bit of squeeze by removing redundant power pins (there are ground and power pins on each corner), but that would be on the next version.
Adding RFM22B to the motherboard could prove to be a bit of a pain in the ass with this package, but I can still try.
For now, I'll start working on a basic CC3D style motherboard, then maybe a PDB...