one could do with something—
1. one could make use of or benefit from smth.:
- You look as if you could do with a wash and brush up.
Cf.: one could do without something—one could dispense with smth.; one could manage in spite of not having smth.:
- There were times when physicists ran from philosophers, being sure they could do without their advice and recommendations.
2. is used as an indirect way of asking for smth.:
- I could just do with a nice cup of tea and a smoke.
one couldn’t do with something—one couldn’t put up with or tolerate smth.:
- I just couldn’t do with only one pair of pants because I would have to do laundry too many times.