Great idea. It will indeed be "much more interesting."
For example, there might be a need for a specific, albeit unlikely, event to occur 10 times in a row during a battle. Let's say the probability of this event is 0.5.
With save/load, achieving this sequence is not difficult – it takes about 20 cycles.
Without save/load, it would require 1000 attempts to play the battle "in one go."
So, we'd get the same frustration, but much earlier, in the simplest battles. Does anyone really need that?

* - I'm not being overly critical, I swear.

Well, yes... but we shouldn't have to do that! 1000 attempts... are there really players who will still try to "fish" for something?
I know you're a strong offline player; would you really try to "fish" for something?
The point isn't to create frustration, but to completely eliminate the possibility of unrealistic battles like "Minotaur vs. 10 Cyclops!" or "fishing" for a Freeze spell or I don't know, something else... like a Unicorn's Blind.
That is, in offline mode, the Minotaur has a 100% chance to block physical damage,
a hero with Freeze or Slow always freezes/slows, a Unicorn always blinds, and a Beholder casts the spell that's needed!... Let there be the probability of these abilities that the developers intended.
Otherwise, in offline mode, maps are completed in 5-10 days! Try completing the same map online in that time.

And if there are still people who won't be too lazy to use save/load,
there's another idea... but I'll be eaten alive if I write it...
Okay, I won't say it for now – let the players read this and discuss this suggestion first, and then we'll see.;)