Mechanical doping in the pro peloton is a joke. Riders at that level can put out big watts in short spurts on their own. I don't think that any pro rider is going to put additional weight that only adds a minimal amount of wattage, which anything small enough to not be detected by eye would have to be. That inside the seat tube motor would also make a significant amount of noise as it uses helical gears and you can't hide that. Where's the button that engages the system?
The idea of putting magnets on your wheels is crazy also as they are very anal about wheel weight as it is rotational and would be a big drag when the supposed motor effect wasn't on. Which would be a lot because you would still need a battery which once again if small enough to avoid detection would have hardly any Ah so there would be no potential benefit over the course of a pro level race which are pretty long, even criteriums.
Yes, they did find that one in that girl's CX bike but that is the ONLY one that has been found anywhere near a race to my knowledge. I am surprised that anyone that has ridden an e bike for any length of time would even entertain the notion that mechanical doping is an issue. Now PED's, there is another story that is not hard to believe.
There are already e bike races going on, mostly in the e mtb sector, and I can see it becoming a thing going forward even with more road oriented bikes. Whatever format that is come up with will also be tweaked for advantage no doubt. Seems like racing no matter what brings out the worst in some people.