My background: Eve, WoW, Age of Conan, D&D (Online and off), EQ, EQ2, FF XI, Guild Wars 2, LOTR, SWOR, SQ.
Some where good and some I ask myself how an can get that time back in my life.
Do any have traits that are transferable to Zwift?
Ultima Online (the really old school ■■■■ with PvP everywhere) / Earth and Beyond / SWG / Rift / WoW
I really think we should have “health bars” that mirror our heart rates. Something like it gets more red the higher it goes.
I really like the idea of power ups for a little fun, and they aren’t really over powered drastic improvements to your virtual speed but can definitely make you push harder at the end of that interval or on that hill climb.
Like WoW battlegrounds, I would add “teams” that would race other “teams” that had basically the same skill level for 5-10 minutes. 2 vs 2, 3 vs 3, and 5 vs 5. This encourages community and makes you work on your own skill set.
iRacing - same concept as this except with car racing. Laser scanned cars and race tracks. Community of about 50,000 people.
There should be lightsabers. And sharks, with frickin’ lasers.
Ultima Online and Asheron’s Call. Did some Second Life for a bit, but never got too deep into it.
I guess our consistency definitely transfers to Zwift 
Groups / Teams would be good from the standpoint of community. If you have people to meet up with, you are more likely to continue playing.
Team Pursuits around the island would be pretty cool! 
Or capture the flag (using AI to carry the flag)
I have been an avid gamer since the days of SWG. Played most of them from EQ, MxO, GW2, FFXIV, SWTOR, Vanguard…the list is stupid really ha!
Guild/Clubs banners and clothing could also be incorporated and would like to see a communal coffee area. I don’t like the idea much of having VOIP in game outside of a formed group, we all know what its like to have several open mics in mumble/TS when in a raid, imagine what it would be like with a ton of sweaty gents and ladies puffing down a mic…actually might be an additional revenue stream there 
You could also use a sort of handicap system (like golf) but based on authenticated (via Zwift) FTP which would then allow groups of mixed ability to work together in mini competitions, club versus club for shits and giggles or even achievements…
How about adding frame pumps that you can try to toss into your competitor’s spokes
No VOIP in the game. Use externals Like Vent, TeamSpeak, or Mumble. Don’t let the Zwift developers waste their time on something that is already out there.
Really like the idea of Capture the Flag.