I disagree with the general vibe of your post although you do make some valid points.

They do accelerate faster than bikes, because they have a lower mass (or due to gearing). This lower mass is very important when you have a collision - force x time = momentum. You can very quickly take the force out of an impending collision with a scooter, compared to a bike.

Due to this fact, it makes turn indicating much less important, but I agree it is a slight problem. For comparison though, pedestrians don't give turn signals, and scooters here are in an uncanny valley. You can in fact hold your scooter by the middle of the handle bar and ride one handed, but I wouldn't recommend this. I however can quite easily drink a can of drink while riding my scooter - but this is not a novice behaviour for sure. My feeling is, indicating is a nice to have, but won't be forthcoming, and it is upon the rider to be aware and give way to all other vehicles and pedestrians. Due to speed and agility, scooters are at the bottom of the right of way totem pole, and that's ok.

Visibility is pretty well catered for on an ES2 with lights all over it, and most scooters now have some lighting front and back. This is a non-issue really as they are about equivalent to a pedestrian even when accounting for speed (which again should be moderated by the rider).

Small wheels are not good for potholes, and also, they have pretty horrible traction in the wet. That said, this is a rider safety issue more than third party. Some wheel bases are getting a little bigger to cater for this, with suspension as well. This is not so bad as to be prohibitive. It is prohibitive for wet weather, but not at other times. The great advantage is that quickly jumping off and breaking with your feet on the ground and just running is a perfectky fine stopping mechanism.

Average human sprinting speed is 15.9mph and top speed (Usain Bolt) is 28mph. These are effectively just like having people sprinting everywhere. This also leads me to think that a helmet is not required, however there should be a strong push to bring their weight down (which is difficult due to durability/ cost). Most durable decent long distance scooters are about 12kgs with the lighter side short range coming in at around 7kgs. This puts the average adult riding a heavy one at 15mph at a total weight of 74kgs.

For comparison, a scooter has a stopping distance of Braking distance 3.9m on dry asphalt from 12.4 mph and 165 (74kg) pound person. (Shorter if you jump off). By comparison, a bike which has a fast commuter speed of 30mph has a stopping distance of 10.4m. Average commuter speed for a bike is 20mph, with a stopping distance 4.62m (http://www.exploratorium.edu/cycling/brakes2.html).

I agree we don't quite have the infrastructure, but I wouldn't let perfect get in the way of good enough as we transition there. Footpaths in most cases are good enough, in some cases roads should be used, and in some cases it should be bike paths. The sensible choice is always clear to me, but maybe not to everyone, similarly, the etiquette is not set yet.

I think for now, more effort should be done on establishing laws - no helmet is ok, lighting back and front is required, bike paths when available, footpaths when car traffic is high, side of road when pedestrian traffic far exceeds car traffic so long as car traffic is under 35km/h in high density areas. Passing pedestrians should aims for at least 1.5m and not be travelling in excess of 8km/h while passing. Pedestrians always given right of way.

Cyclists routinely overtake me when I'm on my scooter, so it is just false that they don't go faster on average (and stats bear this out) 20mph vs 15mph. The main difference is gearing. Going up a hill a scooter will often be faster (up to a point where the scooter won't go up the hill. Flat or down hill a scooter will generally be a bit or a lot slower respectively.

Thats kind of my initial thoughts, but I'm sure you could do better.