By switching to a normal chain ring there is no way to make it retro compatible
I don't see why that would have to be the case. If the mounting points were in the same place relative to the centreline of the BB it should work. There's no incentive for Bosch to do that though and it may make the new motor bigger than necessary.
I'd be interested to see the form factor of the Active Line motor that uses a normal size chainring.