Unfortunately I have seen a V10 with a motor bolted onto it. The battery pack was lipo in a camlebak, with leads connecting to the battery.
Ever seen those pics of an iphone burn after crashing? Yeah, I thought that, but my "feedback" wasn't welcome.
The one I'm referring to is a bolt-on kit. The battery sits on the downtube or water bottle from memory adding weight lower down but. The problem is that the motor generates bit too much torque coupled with the weight and fractures the mounts. The MTB bumpiness wouldn't help the electrics either. I think it still early days for these now.
I wouldn't want any battery strapped to my back if you have an off and do a Galaxy 7 note impersonation.
My take is that they are under regulated, especially seeing some of the "custom" ones getting about. Most are illegal for on road use, but that is where they offer the most benefit.
I have also encountered the 'tourist effect' on trails - where the ebiker (rental car driver) can go fast in a straight line, but can't corner for $hit. This isn't because they don't know the trails, but because they don't feel the immediate effect on them they don't learn to ride smoother.
I think they are limited on the motor output size. How you would police that is anyone's guess. For good or bad they will have to co-exist and they won't be going away. Having a bit of electric assistance for hills is one thing while having a full on BSO powered by batteries is another.
I agree with the tourist effect. People seem to want to get out and see far away places with minimal effort or discomfort. Sadly reminds me of those high end SUV commercials with the marketable family seeing a rainforest while strapped into nappa leather seats with dual zone A/C.
I both prefer the e-bike to the 2 stroke bogan bicycles after said rider has lost license to drive their Falcadore due to a DUI conviction.