I, for one, wouldn't be able to play the game under those circumstances. It usually takes me between 8-12 hours to play a turn, and my gaming time is broken up into 1-2 hour blocks of time, with the turns are played on either of two different computers (home and work). Obviously, it would be impossible for me to ever completely play a turn, since saving it would then end my turn.
From a technical standpoint, what is needed is a server check for time stamps and file identifying hash marks when the turn is saved at each intermediate save point. Then, another server check when the turn is loaded, to prevent reloading of an earlier save point, and thus preventing being able to replay some portion of the turn. In my opinion, this is what the Slitherine Server system should be modified to accomodate.
What isn't, and shouldn't be, a problem is the loading of any number of sequential, non-overlapping save points, so that a player can play out a turn over multiple sittings. Expecting and forcing players to play out a complex game's turn in an unrealistically short amount of time is self-defeating. As an option to speed players, I've got no problems with it, though I would never be able to play this particular game under such conditions.