I think that was
@Kremmen's point as well (and I agree with that). I've only reacted to your "accessibility issue" (actually even A139 uses LED on one of its remote channels...). The "base" unit then does need basically nothing expect SDcard slot and power connector.
Not using parking cameras as a dashcam I see as a missed opportunity for every car manufacturer. But still, if somebody tried that, it's more like a half-baked solution, probably only Tesla was able to handle that perfectly. Here is BMW's approach which, despite offering 360° surround view for parking, it downscales the resolution of cameras a crops it to look better (it's usable but only as an additional evidence next to a proper dashcam), not to mention it's only available during drive.