Well... my original answer was "play warhammer frpg lol", but I knew that wouldn't be well received...I mean, that's fine... but all that's going to happen is that the party will wake up in the morning and have the casters with healing spells cast all their slots to heal people up as much as possible with what magic they have... and then more often than not just wait 24 hours without continuing the adventure in order to let those casters get their spells back. So unless every single adventure is on a timetable... the results are going to be the same-- the party will only go out to adventure when they are at almost full health and have their full suite of abilities.
That's always been the issue... DMs have this idea that they want the players to go out at reduced strength because it seems like a compelling story issue-- the ragged adventurers striving forward even when tired and hungry-- but no players ACTUALLY want to do that, because that story gets really old, really fast. And if they can avoid it... they will.
The fact of the matter is... ANY available "fast healing" that is available to the players in the game world will be scavenged and used as often as possible. Even if gritty natural healing rules are used and there are no healing spells in the game, but there ARE healing potions or rangers/alchemists can create balms and salves and so forth... they will do so. And they will stop at every temple and scavenge every plant they can (especially during downtime) to acquire as much of it as possible, and USE as much of them as possible in order to top themselves off before going out to risk their lives time and time again.
If a DM really has this thing in their head about continually wanting the party out to adventure at half-strength and "fighting against adversity"... D&D isn't the right game to be playing. Because there's too many avenues to get around it in the rules, and the players WILL travel down every single one so they won't have to.
(seriously though, the warhammer frpg system doesn't have to be used in the warhammer setting. I've ran great campaigns with it on a pseudo-earth world, where I wanted a somewhat lower fantasy feel. I seriously believe that gamers should, after a while, try other systems. Either they will find something better suited to their tastes, or it will increase their appreciation of D&D)