I wonder if you ever played a game with no save except when you quit. I know some popular game like Diablo or all mmorpg have a similar system but the penalty is moderate when you die even if very unpleasant.

With no save, just one error and you could spoil your game, that's your error and the effect can be huge not just few xp and gold penalty. I agree you have margin, but just a bit of optimism after a good series of battles can be enough to not evaluate well a battle or make a series of disastrous error.

Also I disagree that with sac only you do the job, it will be rude to manage constant sac with no res from gift or res spell.

u can cheat with sacrifice

casting upon a giant
it will not die
but u have free life points;-)

Few free life points, that's just theory, because in practice that will be very slow and very tedious, nothing better to start doing wrong thing and end spoil the game. :)

Personally, I would prefer the fastest time/no casualties/highest score challenge simply because these goals could be seen in the final record. As for no save-file abuse...

To each his own, I guess. I did a no save-file abuse before for Resident Evil 2 (in fact, it's a no saves at all straight run), but that was because for this particular game this unlocked new items for you (it was either a cool new attire for your character or a rocket launcher with unlimited ammo, I forget). :)