I think the simplest and best way to approach the rest issue is simply to attatch long rests to having food. Make it so that you either need to have food in your inventory, or be at some kind of home base or inn before you can long rest. That's what Pathfinder: Kingmaker did and that worked without issue. This lets them make short rests more useful and makes it so (provided they limit food more) players can't just spam long rests whenever they feel like it while not making it entirely punishing to not have food since you'll still be able to fall back to camp, it just requires you retraversing the map.
I'd actually like to see short rests tied to food supply rather than per 2 day as well. Would favor short rest resource characters considerably, but switching some of the class resources (Arcane Recovery and Sorcery Points, fi) to short rest reup would help with that.
To the larger thread point? I definitely don't think Larian should be constrained into making a "5E simulator" game but cooldown mechanics are a bridge too far. At that point you're not playing DnD anymore. Also I think "breaking immersion" has become an incredibly overused shorthand in terms of game criticism. Immersion isn't a boolean, it's a flow. It's certainly something the designers are worrying about, but pointing towards a particular game element/abstraction and saying it destroys the entirety of immersion isn't a useful way of applying the concept. It reminds me of my father saying he couldn't enjoy a film because it wasn't "realistic enough". "They can't possibly be in Russia son, those trees don't grow there!"
I personally find nonmagical cooldown mechanics to be equally "immersion breaking." If my fighter just swung his sword in a massive arc, why can't he just do that again? Because he has to wait a minute in between cleaves? Doesn't sit well in my head. But that didn't keep me from enjoying Dragon Age: Inquisition, because I realized it was an abstraction meant to apply game balance.
