Who is John Galt?

Throughout Atlas Shrugged, Rand keeps raising the question of who John Galt is, so maybe we should look at some of the things that may be known about this character. The first thing that we must acknowledge is that Galt is a character in a fiction. For all the advocates of living life in the manner and style of John Galt, be aware that Galt didn't really do so. The character is a made-up bunch of characteristics and speeches and actions about whom we are asked, as we should be in a work of fiction, to suspend our disbelief. So if we think that such a character could not possibly ever have existed, it's our task as readers to suppose that such a character did exist.
What Rand asks of us as readers is that we imagine a man who is completely self-made. The fictional Galt owes nothing to anyone. He is a highly imaginative entrepreneur. He is clearly able to address other people convincingly. He has the ability to organize many different people into action toward a common goal. He acknowledges no debt to society which comes from his having never received the benefits of the society's institutions. He is the ultimate outsider who is capable of delivering sound criticism of all that is wrong on the inside.
I have heard very little comment from Rand supporters that she builds a case that these are his characteristics. For instance, his entrepreneurship was supposed to have centered on his invention of a means of transport that takes advantage of ambient static electricity. Were Rand consistent with this as the source of Galt's financial independence, it would be expected that somewhere in the novel, people would have taken to using such transportation devices. But this doesn't seem to be the case. This great entrepreneurial success is roughly the equivalent of an inventor of a perpetual motion machine. Was it sold? Did anyone buy one? But, in our suspension of disbelief, Rand has asked us to withhold judgment about whether such a device defies the laws of physics. Galt was presumed to live lawlessly, and those of physics were no more valid than those of society. And why should we demand any physics knowledge from a writer who, like Rand, is just out to convince people of the truth of a particular point of view?