I think MVP is for validating the need. Not for solving the need. If your customer says: we can't actually use your product without features "x" and "y" and the

I think MVP is for validating the need. Not for solving the need. If your customer says: we can't actually use your product without features "x" and "y" and then adds: "when can I get those features?", you are on the right path. You can go on to build the features to get him to use it (Many others will say the same thing and you will see a pattern emerge). If he uses those features as an excuse to say "no", you have failed the validation test. You need to look for other problems to solve.