If we converted to region level realms and used managed populations via sharding and cross realm then time zone wouldn’t be an issue. We could just peg resets to regional time zones and as far as “peak” play time your peak would average out over a larger block.
That is to say all east coast players will generally play when all east coast players are on, PST to PST, and so on.
These divisions are arbitrary. If we can handle the processing of real time data via cross realm (which crosses multiple datacenters) we can surely connect the economies togather. Which is all connected realms are. They are the stitching of the economies of realms into a larger block. The Auction House stacking mechanism and community mechanism makes this totally doable to guilds and banks regionwide.
Arguing this in more detail in another thread: #ConnectAzeroth - The Final Realm Connection