can this not use a single center motor with a shaft, just replacing the current structures? It won't be that big savings as it is in electric vehicles, but it could reduce some complexity and unify architecture of electric and ICE?

This proposed power transfer mechanic linkage can't handle angular differences between the power plant and wheel, so you would end up with broken mechanic linkages and torn shafts.

Non-spinning-shaft power transmission (doesn't really need to be electric, could as well be something like fluid power transmission like hydraulic or pneumatic power) dodge this by putting the power plant in a way the angle between power plant and wheel can't change.

If you have a single central motor and shaft, then existing CV joints work just fine. This is useful when you want to have a separate motor for each wheel, because it lets you put those motors closer to the wheel. There is then space in the middle (where the shafts went with the single central engine/motor) that can be used for something else not related to the drive train.