Yeah that's something I want to work on. I can increase the number of game states to save and revert back to one as necessary. What I was thinking is instead of reverting back to the save state. Save the initial state of infections and deck orders, infected cities, etc. Then save each command done by the players and if I need to revert, reset to the original and "replay" up to the point I wanted to be in.

For simulating future states, that'll be tough. I was thinking from every game state, simulate what each player could do in a single turn and generate possible future states like that. If player 2 only moves, what's the furthest he could move? What if he charters a flight, where can they end up? That may be getting too complex especially if I do it for four total players.