It sounds like a very interesting idea and I'd be interested in seeing it done.
I think, so long as the belt is tight enough, that it will keep the fabric in place. I can't be sure of that though, as it's not an area of my expertise.
I'm not sure, however, that this will actually get more men interested in kilts, despite the cheaper cost (although I wouldn't mind being wrong!). I just think that the effort of putting it on like that every time is too much for most men to care for, especially when you're talking about the modern kilt market and converting men from jeans to kilts. Although, the Cheater Pleats might help with that. But I think this would probably be a niche market for those that are already into modern kilts, and would like a phillabeg but may not want to use tartan.

Hmm... this has got me thinking about a "contemporary great kilt".