Why are there just 3 servers for a whole continent and all of them located in one and the same country? Especially if surrounduing countries got a pretty bad connection to said country.

Everyone should get at least one LQ option. Friends of mine often have to stream at LQ to make it watchable for those who still have to deal with bad internet, bad routing or bad devices. This is sadly still more often the case than it these days should be.
And those who who usually don't have a problem to watch a 1080p/60fps+/6k+ stream have to deal with it. And those are sadly the first ones leaving once they see some stream at 480p pixel garbage.
I myself would also be bound to stream at LQ for the sake of my friends who would want to watch.

The ad system ist perfect without any kind of midroll ads garbage.
Twitch makes tons of money from normal ads already and through subs. Midroll ads are completely not needed!
I just got ads every 15 Minutes(!) while watching a speedrun. Guess what? I missed key content. Yeah thank you very much. This is not frigging Television!

Best overhaul: Leave everything as is.
The ad system ist perfect without the midroll ads garbage.
Twitch makes tons of money from normal ads already and through subs. Midroll ads are completely not needed!
I just got ads every 15 Minutes(!) while watching a speedrun. Guess what? I missed key content. Yeah thank you very much. This is not frigging Television!