There's no need to make things complicated. This is not that hard. It’s not Larian’s first time at the rodeo.
They’ve done non-regenerating health and mana before, in Divine Divinity. That was in real-time combat, though. Healing was done through a magic spell or potions (which could be consumed while paused.) Even if you drank potions in real-time, you could bind that to a button and spam it.
I think potions in this game will work fine, especially since they’ll take action points to use, so it’s a trade-off in combat, but relatively free outside of it.
