Considering that food often only heals 1 or 2 hp a pop, if you changed food consumption to a rest-based mechanic there would be almost zero reason to use it anymore. Especially considering the relative rarity of potions, players would be encouraged to spam long rests (to make sure their healers weren't blowing all their heals between battles) which is already a small issue.
Unrestricted longrest is another issue Larian should worry about.
There definitely should be penalties for player resting too often.
Or just outright denying longrest, until party actively plays for about half an hour, or pass one battle encounter.
Also, some food heals over 20hp. Which makes even potion of greater healing really worthless.