Currently, nothing respawns and there are no random encounters. So anything but the current model is just asking for devs to waste their resources for players to waste their time. You can already manually walk through empty rooms back to the surface if you want pointless travel time.
Right now having to click to long rest is a waste of player time because you can do it whenever you want anyway. If long rests are going to be nothing but pressing some buttons to get HP and spells back, they might as well give you an auto long rest after every single encounter. And then go through all long rest abilities and spells and nerf everything. And of course remove short rests completely.
Maybe easier and safer to just make a rest system that is immersive and mechanically meaningful.
