Nice thoughts...
There should be an option to slow down instantly and just a little bit compared to breaking.

I'm thinking about a different thing...
Acceleration via motion sensor

I can confirm all of these points are happening on my android, too.
The first one happens since today.
I often notice that crashes with other karts make only me stop, turn around, or smash over the track while the other kart is driving away...
Pings are horrible at one race and fine in the next one (setting: optimal). Might be a problem with overseas players...

Yes, balancing in item mode is horrible.
Skills (incl. track knowlege and using/avoidig items at wise track positions) don't count anymore. Is't more like throwing a coin to win or to loose.
Players should get hit once at a time only incl. a second of invincibility.

We need old items back...
The devil (switched controls, now incl. smartphones just switched steering), cloud (hide player and track) and 1st-missle need to come back.
The lightning should hit all players in front of the user only, even in team modes. But it should have less effect (don't stop karts, but maybe block steering for a short time)

I was playing a lot of item races..
The balancing system is way to unfair. Skills don't count anymore. From first to last and vice versa is a question of 2 seconds. There are no longer racers arriving after 10 seconds. Very often all racers arrive within 2 or 3 seconds.
It feels like a mixture of (of course) luck at items 60%, 5% skills and the rest % get lost because of balancing..

There should be a short time of invincibility after getting hit to avoid a double or triple hit