There seems to be some benefit to having a formal deal in place.
Yes, but the "in place" part is what's in question. You can sign a deal, and the next day Trump can say it was a bad deal and it's off the table... again.
Much of the stuff he's bickering about now are things HE negotiated during his first term! He'll never be happy, and we have to stop wasting time on this baboon and seek partnerships with leaders who aren't complete assholes.