Well - as MODs are optional - and I could deactivate it anytime - I would surely try it.
Still to make it more interesting (respawning enemies) I would like to add some variability to the respawned army... like:
1.) It's strenght will be more relying heroes stats / level (so if you return after you are stronger, even the respawned army will be stronger)
2.) It will increase in power regardless of you actual level (so the respawned army will be stronger even if you are not)
3.) If the army was led by hero - let the hero learn the spells you used in the previous combat + increase his INT (also give the hero option of casting twice if the neutral hero is "mage class")
4.) Add full new stack of units - could be based on country (in elven lands some elves, in dungeon dwarves or beholders)
5.) give the enemy hero (if army was led by hero) some artefacts - but you won't get them even if you win (just to give some bonuses to neutral heroes from artefacts)
Still, even if any of my 5 points would NOT be possible - I would try respawning armies - but I am afraid that it would be useful only for upgrading items (after x battles you get something)
Otherwise it could be bothersome to fight on 30th level 20 archers and 30 thorns...
(just lost time)