I tried something kind of cool with your (Only Save When Resting) idea. It's called Skyrim Requiem - Sixth Sense Mode.

Skyrim Requiem - Sixth Sense Mode Rules

Your character was born with a natural sixth sense that comes in the form of dreams. You save your game upon waking each day and then you live out your normal day. If you happen to die that day, doing whatever, you simply reload your saved game at the time you woke up, and everything you experienced during that day was just a dream... and a warning. Knowing that if you go back to the place you were just at in your dreams, you could die, just as the dream showed, it's up to you to decide if you want to risk. If you die a second time, even after the dream's warning, then you're permanently dead, just like DiD.

Now, if you make it through the day and sleep, you save your game again upon waking and a new day starts, and you are allowed to die one time again. See how that works? This is going to be my next play through and I'm very excited about it.