Something closer to this is doable. Normal difficulty should be 5e rules, hard/tactician something along the lines of what you stated, and Story Mode gives you an option to hit that prompts “rout/end battle” where the party automatically kill off/subdue the remaining combatants. This would address what some feel is the boring/inevitable waiting round after round to strike that final blow to finish off a lone goblin.
I’d rather that, than trying to divide development time and resources creating a whole new battle mechanic.
