Well, I LOVED the training system, so sad it was taken out. Not askin for the old system, but could be an added bonus.
I do like your idea of voting, but this could be quite hard and people could exploit the system so we have the same raids over and over and over again. I personally like new events to be a surprise, and for the reason above I don’t think it would work.
The idea and the mechanics of your third idea are already in game ( kinda ). You can see if a raid is in progress if you have a mon in a gym that the raid is on. But maybe a tiered system : bronze, you can see tiers 1 and 2 at raids by looking in your badge case, silver, tiers 1,2,3 and 4, and a gold badge would allow you to see all raids in eggs and in action at that gym.
A scanner? Very, very unlikely, as it ruins the idea of the game, but maybe in the nearby bar, in addition to the Pokéstop Pokémon and raid list, there would be a system that shows you wild Pokémon and how far away they are, with priorities to rare and uncaught mons, similar to the footprint system when the game first started.
Overall I think your ideas are great , but not all of them would help the game progress at its current rate.