A colleague did his and didn’t need any welding specifically. Just some minor modification to the motor shell itself.
The newer casing design is much smaller, so avoids the issues posted.
Personally though, I’d just rebuild the wheel with a hub motor and some Alpine spokes and you’re good to go.
Apparently it's the frame shape - the motor doesn't fit under or above the BB without some kind of banging about and welding:
https://endless-sphere.com/sphere/threads/christiania-bike-conversion.66631/