Hi Ivy!
Have a look at this bike, it does have the bafang ultra max, rohloff and gates belt! It is possible!
https://www.orangebc.com/de/produkte/fat-e-bikes/steinerdesign-ultra-ebike-fully-27-5-plus-rohloff-gates-karbon-riemen-speed-pedelec-zulassung.html
Posting this here, although id love...