1). Personally, I don't care to play against premades, the problem is to play with it as I illustrated, for once, you just have to play yourself with premades to not find yourself in this situation, you can very well fall in a part with only solo players and the team opposite itself can be very communicative while yours not without reason. After that it is my personal opinion but yes why not if it allows to be fairer but it may be "a little too much".
2). If they do that, it will be the same, everyone will play mirage, I think that indeed this choice of maps for the premiums is a shitty system, there should be no votes and add random maps, this which would also make the game more competitive and the players more complete.
3). + 1 and moreover as an argument for those who will say that interaction with others is part of the game, I would answer that there is a Faceit room chat, so they can use it.
4.) + 1
5). + 1, after for toxicity unfortunately I think it's something immutable in the game, there will always be toxicity somewhere