Then whatever MCU you want to use is up to you.
It would be the bees knees if we could even get the pinouts to support the 32u4 version and also all of the other ones, need to see if all the GPIO line up.
I think this is the answer. It makes it as cheap as possible to produce, maximum development flexibility, all of the usb and lipo charging is handled by the Feather module. And the wing has a lot of opportunity as the adoption of the feather standard is pretty broad. Particle even has cellular modules that would work, Arduboy as a cell phone.
EDIT: I suppose the compatibility to the 32u4 module is less important as the OLED will require a new library anyhoot.
EDIT: external ram and flash might be a pretty sweet idea too, although several feathers come with sd cards. I guess we can have the pads, and you can elect for Arduboy 2 fx which will populate the external components.