Unfortunately not. Today, I will be moving the Wokeby trunk extension and frunk sealing from our 2019 to our 2021 i3 which will make my signature valid.
I will also be swapping the 428 wheels with wheel locks on our 2019 with the 429 wheels on our 2021. The rear tires on the 2021 are new with <9k miles on the fronts while all 4 tires on the 2019 have been driven only 3k miles, so essentially a wash for average tire wear.
I'll swap the LFP 12V battery and 12V system logger on the 2019 to the 2021.
I'll move the BMW i Function Cover (protects the cargo floor and rear seat backs when folded down) from the 2019 to the 2021.
I had planned to swap the 2019's dark oak dashboard trim with the 2021's light eucalyptus. However, my wife made a valid observation that the eucalyptus is an attractive transition from the Galvanic Gold exterior to the dark tan Giga leather trim even though the oak is a better match to Giga leather.
I haven't decided whether to swap the 12A occasional use cable (OUC) from our 2014 i3 with the 10A version in our 2021. I have instructions for converting the old 12A OUC to a dual-voltage EVSE, but my charging circuit has no common wire which is required for the modified OUC to charge at 208-240V. I believe the newer OUC's have additional protection against an overheated 120V plug that earlier OUC's don't have. I have a 120V 20A charging circuit, so using the 12A OUC doesn't heat the outlet or plug dangerously and does charge a bit faster than later OUC's. Maybe I can find instructions for converting a later 10A OUC to a dual-voltage EVSE.
The digital compass logic should be in the mirror housing rather than in some external controller, so I agree that both mirrors probably share the same power connector and swapping should be plug and play. I'd have to split the plastic mirror housing to gain access to the interior. The two halves of this housing snap together, so if any tabs break when separating the halves, a new ($$$) housing might have to be purchased assuming it's available as a replaceable part. Being able to snap into place so much on an i3 speeds its construction but risks breakage when disassembling. I'd rather remove screws instead.