I like this concept of a minimal core camera which has a huge sensor, the logic board, a battery compartment, and then mounting points for accessories to customize it to the use case.
Lack of in body image stabilization is difficult, though. It makes sense for a minimum size camera but IBIS is amazing when it’s working well.
Ever looked into digital backs? Basically what you are describing. Sometimes minus battery - the (old) mega vision backs are just a sensor, FPGA, and firewire cable out to a host!