Cutting the GC out of the middle will result in your getting no more work from the GC. If he's getting you the work, let him put whatever he wants on it. Most customers deal with the GC, there's generally a big mess if they try to put the pieces of a construction
job together themselves.
I'm working on a church that did this. They made a 3 month job last over a year by "trying to save $". The Construction Loan expires tomorrow, it'll cost them big $. They're in deep manure, and still aren't close to completion.