One concern with mid drive e-bikes is that if the motor breaks in ten years, probably there is no exact replacement available. But do the manufacturers keep the same interface for their different motor models? For example can all/several Bosch motors fit the same frame? I assume e.g. a Shimano motor certainly won't fit a frame made for a Bosch motor? Are retrofit kits the only ones where the frame is not specific for one single motor model?
Which leads to the question: Did someone make a compatibility chart of which motors are interchangeable?