After riding 50 miles over my 1st Zwift weekend, several suggestions (which have probably been suggested by all the more experienced riders before me):
Have some type of visual indicator (flag, line in the road, something) to indicate the start of a timed section (sprint and KOM climb). Took several laps to figure out where these started, as you add new courses will be hard to do from memory.
Remove the AI from the leaderboards. Like having them on the course, but it’s annoying to have them listed in timed sections.
More analysis during a ride - like avg/normalized power for a lap/timed section, avg wt/kg, etc. Also show this stuff by lap after the ride.
For us on lower tech trainers (I have a Kinectic), maybe some type of indicator to force us into a big ring on uphills. You can verify this by looking at our gear ratio, which can be approximated by our cadence and wheel speed.
Add an arrow to indicate which direction you are going on the maps in the upper right corner
Mass start race - maybe teleport all interested parties to the start line once an hour for a large race?
Of course, add the stuff you are probably working on: more courses, training mode, more appearance customization (like hair color, hair type).