No, Bafangs don't have walk assist.
No, derailleurs do not get "unhinged and rattly over time, with multiple failure points" unless you're using really crappy cheap derailleurs. You seem to be conflating derailleurs with cassettes as if they're the same part. A derailleur will far outlast a chain and cassette on an ebike, and the latter two pieces are cheap and easy to replace.
I also don't buy that an IGH under the same shifting loads is going to last 10 years without rebuilding or replacing.
You make an awful lot of blanket statements about certain components because you seem to prefer different components. Good on you for your preferences, but your comments about the stuff you're not into don't sound like they're derived from using them.