hmmmnnn. I'm guessing you have muscle contractions during a seizure? Perhaps the only thing you need to worry about is the throttle. Perhaps a hand grip which is activated by a twist would be more dangerous than one which is pushed on by the thumb (like classic bike gear shifts).
Pedlecs are another option, however they are not that popular. They only provide power assist with each pedal stroke, so if you cease to pedal, the ebike/scooter stops going.
I've retrofitted an old adult sized tricycle with an ebike kit. It has one of those oversized seats. It is so comfortable, I find that I enjoy riding lengthy distances that much more, however I wouldn't know how comfortable a large scooter is. The storage space in the back basket however is substantially larger than a scooter. With the ebikes/etrikes you are not so much limited to the road and can take all the bike path shortcuts. Over the summer a 100km trip both pedaling and powering, is no problem, you won't break a sweat. Especially on a three wheeler. reserving the power for hills can really ease the ride, and lengthen the distance you can get. It's the hills that make a bike ride uncomfortable, plus sitting upright. I did witness a scooter break down and those guys when they break down, have a miserable push ahead of them. When an ebike breaks down, it's not so bad, and parts such as chains, or tires are available everywhere, in the event that happens.
The scooter vendors in my area, seem to be selling road legal but bike path illegal scooters. So, they are capitalizing on the ebike trends, but in reality they are not welcome on the trails and such as the ebikes are.
I personally do not enjoy riding in traffic next to cars. I'd rather take the sidewalk or a bike path. Oddly enough, a long empty rural road is great riding, but as soon as there is a high speed limit, cars can wiz right by you at uncomortable speeds pushing you off to the shoulders, ebike or scooter. If you have extreme hills in your area, go with gas or something. I've seen people with mini motor bikes. Mountain bikes with loud gas motors, and I am sure there is are endless options out there. I live near an escarpment, so I have to make sure I plan any trip properly when conquering those hills, otherwise the batteries will not last you long at all. In fact, on a brutal hill I'll opt to walk the bike up, rather than kill the batteries. Not too many hills are brutal, I'm referring basically to mountains. Ones that put cars to the test.
If you go the ebike/etrike kit route, the only major pit fall is that the motor cannot attach to an aluminum fork. It needs to be steel and preferable re-enforced if you are going to push the limits of the bike.
If you search youtube, 'Hybrid Electric Trike 130 Miles Per Gallon ! Bicycle! Tricycle! Gas Bike' he has an over the top hybrid thing happening. There is alot of good stuff on youtube.