You would find supplies as you complete encounters. The game would be designed to give you sufficient supplies when you reach a safe spot to camp. You can still save any time.
This would be for the hardest difficulty setting only. If you want a butchers Shoppe full of meat equivalent to 5 long rests after a goblin fight you can still have it on a lower difficulty setting.
The party composition problem is also resolved by simply turning down the difficulty to walking grocery bag mode.
