I don't expect this to be a popular opinion among the hardcore PvPers who complain about too much pvdoor. But as for the rest of us...
For a period of ZOS' choosing, please allow a Cyrodiil invasion to occur anytime one alliance has highest pop, owns 50% of the map and 50% of scrolls. Feel free to change these parameters however you like.
This invasion would consist of Elite/World Boss-style armies (4-12 unit AI group) of multiple world bosses that can attack and take over resources and keeps.
Make these elite enemies a big challenge that can't be conquered without a 4-man or 12-man group (provide enemies at both difficulties, pretty pretty please so I have a reason to get my PvE friends as obsessed with Cyro as I am) and have these enemies drop oversized rewards. It can be as simple as 5-10k tel var or something new like a 5 piece collectible, furnishing or mythic item. Do NOT make these just sitting world bosses. Have them roam like the bosses in Deadlands but they should work like an army and be as difficult as Dragons in Elsweyr.
Alliance War is literally the best MMO PvP game I've seen and it has sooo much potential but the last edition we had to PvP was a Battleground years ago. We've had temporary test events, we've had double AP events but no new story, no new concepts of any kind besides sets and builds. Alliance War players want to be in Cyro 24/7 but we are pushed out because there's literally nothing to do during EST day time bc one alliance will always be there to take over the whole map.
Give us a reason to go back to Cyrodiil. Give us something to play when the map is dead. Give us a REAL Daedric invasion!!!!!