I think multiplayer is doable with only minor modifications to the current system, just have it to where time warp is only in effect when both parties would be using it, with the addition of it can also be in effect on your own island. Currently there is no purpose for having full control on your own island unless you are actively defending it from an attack or you have units on the island itself (which get destroyed when you leave it anyways) so time warp could be possible while you're just sitting there waiting for productions to grab from your stockpile or something, while your enemy is free to move about the island chain, or vice versa.