I think it's a very bad idea IMO.
People like me and many else I know would just get so frustrated by something like that,some would even give up playing the game.
What if a battle is too hard,and last save was something like 2 quests or dungeons ago,and I'm dying again and again in that same battle ?
Why to be punished to replay again the quests I already completed succesfully ?
The only games I know of that had limited saves where the classic Resident Evil games,but they where games you could complete in 3 hours.
I can't see this working in a game that we are going to play for 300 hours.