Haven’t read entire thread yet but I’ve installed Swytch front hub kits on Bromptons. I’d run, not walk, away from eBromptons with any system.
Don’t get me wrong Brompton is a very nice bike but simple things such as handlebar real estate often require massive changes to $$$ nicely made components.
Best hill climbing efolders I’ve assembled - Bafang 750/1000w BB drives. 20”Swift or Dahon Speed 7 each handled the 68mm BB install just fine.
Dahon folded normally but the Swift was limited by a small amount hitting the drive. Still folds enough to qualify for rush hour transit tho.
Great hill climbing but as Chalo noted much more maintenance for chain, gear selection system. But, chain breaker, links + easier flat tire repairs more than make up for that deficiency imo.
Lately, I put 1000W DD hub in the front wheel of Swift Bafang 02 mid drive. Now that gets up and goes like nothing else. Overkill for urban commuting but longer suburb routes with hills it’s well worth the trouble. It’s also nice to have DD reliability up front if/when the chain drive system acts up.