Even with it well stalled you should still be getting a few amps at 15mph. If you still can't measure anything you have a measurement problem and you need to sort that before messing about with new stators.

If you by any chance have access to the 6 phase connections, try it in delta or Jerry connection and that should bring the cut in up to something reasonable. If not then try a big increase in air gap, get the speed up to a point where it at least comes out of stall in low winds and try some line resistance to get it up to a better speed in high winds.

The #12 wire is not too bad, it's not going to give the best results in high winds but it may do what you want and give good enough results in normal winds.

Just to prove things for now, drop off one rectifier lead, it will not stall single phased. If you still cant get current and the speed comes up you have other problems to sort before going off to build new stators. The thing is to collect as much information with what you have, before starting out on a rebuild.

I don't think you are so far off that it won't work, just keep investigating and sorting data. It must surely be doing 4A or so even hard stalled at 48v in a 15mph wind. I still am not convinced that you haven't got a measurement problem.