The people who do not save can't reload and cheat. The Tiller HPS games have an option to disallow file save and this is how I play people I do not know.
Sorry, I'm still struggling to understand the issue, are you talking only about PBEM or server games?
In server games, once you save, you lock-in the in-game status on the server, and I don't see how cheating is possible with saved games. On the server, my understanding is that cheating is only possible if you play awhile, don't like the result, exit without saving, and then start over. I usually play for a while, save the game (lock in the status at that point, reopen the game, continue to play, save, wash and repeat... Playing for a couple of hours and then losing the turn because of a server problem, computer crash, etc. just sucks!
I only play server games, but mainly for the convenience (no fiddling around with attaching files, etc.) but the cheat protection is also attractive.