The problem is, there is no "perfect" solution without a server-side solution.
The way it *should* work IMHO in an ideal world is this:
* Civ would have a checkbox for HOF mode. In HOF mode, you are a client to a dedicated server run by Firaxis (or the HOF staff) and play your entire game as a single-player online session.
* Since you can't play without the server, you can't reload or hack your savefile.
* There are no local save files. (preventing some of the more obvious HOF exploits)
* A disconnect would trigger an immediate save on the server, so if the client crashed or lost connection, nothing would be lost, and *no steps could be replayed*
* Multiple people could play from the same starting autosave in "Competition" mode.
Advantages:
1) This would allow you to save and quit repeatedly as long as you didn't reload. This would make playing HOF games WAAAY easier on those of us who can't play for long sessions. As it stands right now I have to leave the game running with my computer in sleep mode for 12-24 hours, and that eventually causes audio and graphics corruption, sometimes crashes. In fact, the only time you will see my logs show multiple sessions is due to saving and quitting because the graphics had become unplayable. Part of the reason I do this is because I like to play in "true" hardcore HOF mode. (1 session) If there's only one session, it means you never reloaded.
2) This would make it much harder to cheat. Right now there are ways to cheat deity challenges and HOF games that the staff cannot detect or prevent.
Disadvantages:
1) playing offline would be impossible for HOF
Currently, Deity challenges can be reloaded over and over from the starting autosave. Meaning you can play through, learn the map layout, opponents, ruin locations, etc. and then replay until you get a great start, or luckier outcomes of mid-game randomness. I know most people don't do it, but the fact that some do (undoubtedly) ruins the fun for me.
HOF is subject to similar malicious behavior, because if you save infrequently enough, there's nothing but honor to prevent you from reloading those infrequent saves *as many times as you want*. However, because the first 30 turns are the most important, usually, it's harder to maximize the start. So it's *somewhat* less susceptible to exploit.
Both, unfortunately, are subject to the "play through the whole game, learn the layout, then replay from a mid-game save" exploit, but Deity Challenge is way worse, because you can memorize ruin locations, CS locations, AI city locations, and this *greatly* aids early conquest, and snowball effect from worker-stealing and ruins.
If you don't think this sort of exploit is going on, well, you must be new to the internet. Having worked on a large number of multiplayer and MMO titles, I can promise you, this is going on right now in HOF and Deity challenge. Any game that can be exploited *is being exploited*.
So, for now I prefer HOF. But only barely. My idea would be better. WAY better. Firaxis should hire me to implement it.