So, does this singer/songwriter really need this band? It's his music. I say (without being there to truly understand the situation) that the singer/songwriter is the top dog. Good musicians are a dime a dozen, so if the band's not on board, fire them. Seriously. Again, I realize that I don't have all the facts and whatnot, but what does the band really bring to the project? The songs are the key, so why should the singer/songwriter give up any of his vision/control? Fire the disgruntled band members and bring in some folks who would actually be happy to play the songwriter's tunes. I bet you could find a whole line-up of top-notch musicians within a couple of days over at the MARSH forums. There's a lot of we guys set up for internet collaboration if that's something that would interest you. I'm sure whatever area you're from is also full of good local musicians willing to participate on a good project for little or no cost.
Just noticed that you're in NYC. Plenty of great musicians lurking about.
Just my $.02, again realizing that I don't really understand the situation. Just throwing out some thoughts.
Good Luck,
Calvin