It all depends on how fast it grows.
What if the player is left without spells and hp after a hard battle
(I suppose the larian bends and remove the healing from the food).
In my opinion, this is terribly overcomplicated.
If the player had just completed a hard battle, a balanced game would mean the next battles they face should
be relatively easy. Thus, a player could get through them with basic attacks and cantrips.
In addition, there are potions and scrolls to heal and cast leveled spells. With the current rest system, after Larian fixes it so that only magic-users can cast scrolls (as in 5e rules), scrolls will be pretty useless aside from increasing your wizard's known spells. If you can long rest infinitely, then you'll have access to all your spells for every battle and thus why would you use scrolls? (Again, assuming Larian will fix the scoll-usage rules)