Have 2 zones be on an island on water, 2 of them are on Dragon Isles floating in the air and 2 underground (or 1 underwater and 1 underground). All part of the same map and flying can be unlocked in the first month or two of expac release.
OR
I'm kinda thorn, I both want and dont want to see 5 zones one for each flight.
But another idea I had was having the 5 flight zones be for leveling (pick your path like legion, Flights are covenants but purely cosmetic, world content and minigame parts relating to their zones, and you can level multiple at max level with resources from the other zones and mainly their zone) and then have the first Max Level zone be either a Twilight Dragon zone, Infinite Flight zone or Titan zone. And patch zones are related to offshoot flights
Honestly with tier sets back and their philosophy for the new system to be only for world content and cosmetics I feel like that might be possible. If they want "borrowed power" just have it upfront initially unlocked an ability relating to the flight or something like that (maybe 3 give passives, 2 actives or you choose what to get between the five). But other than for a Legendary it shouldn't be a grind (even quest based legos were a grind, and I think that should come back).
Guess they might judge it based on ZM performance.
Another thing I wish for is tthe patch x.0 gear sets with outdoor bonuses to be more relevant throughout the expansion. Maybe have a system in place to upgrade them further and have their base iLvL be X but while you are in outdoors zones it is higher (reverse of how PvP gear works). The sets have cool outdoor bonuses but by the time you unlock all pieces if you do any dungeons/raids/pvp you already have better items and its not worth it. Legion had this with class sets, and SL with covenant sets.
Honestly with ZM it seems like they are testing water for having world content
Also if we get a dragon expansion without quests to raise dragons for each flight (like the many questlines where you get a pet, toy and mount while raising a creature) I am going to be disappointed. It is an easy to implement thing for casuals and collectors and they usually love that stuff, and with one for each flight it would be x5. Just add a small chain at every milestone of raising the dragon