I do think the Davis Cup is one of the most pointless competitions in sport. They should insist that you have different players in every match.
I think to be a genuine "team" event you should have to have at least three players in it.
I'd maybe merge it with the Fed Cup and have it so players play a set rather than a match, with a tie-break only when it gets to 10-10.
Nine mens singles matches with three men all playing each other, nine womens singles in the same format, and three doubles in the three different formats. So, basically best of 21 sets.