So, I had issues with my hands and arms too...I really think it's the fact that on an Ebike you just never stop, ever. Even on the climbs I was pushing it pretty hard, harder than normal and my hands had no time to relax. I usually bring my thumbs over the top of the grips, or grab the end of the bars or even move my hands inboard right next to the stem on smooth climbs, but on the ebike I never had the time to do those things.
Bigger rotors are certainly on my short list too, as well as the fork. No real penalty for longer travel like on a pedal bike.