All sounds like lots of sensible ideas. Particularly the HRM pairing is so annoying mid race you can’t do anything about it without ruining your race.
It would be good if you could keep moving while in the pairing screen maybe have a pause button or something for those times where you want to keep pedalling without moving. TTT warmup springs to mind.
There is a new UI rolling out New Zwift Home Screen Update [January 2022] so some of your ideas might already be on the way like the join event directly i believe is part of the new UI and various updates to ride profiles and routes so that hopefully will be a big improvement.
As for the other items you might be better splitting then into separate posts to see if they can get some traction