I don't think that this will be as stable as you think.  I'm seeing a few places where you can expect positive feedback which will amplify minor swings into huge rushes.

Your whole security model depends on backers paying more than the market rate, in hopes of being paid an even bigger premium later.  Since they only profit when the value of the backing instrument rises, they would be better off just holding that instrument directly, rather than using it to go upside down in a new venture.

At least that's what I'm seeing from reading this thread.  I'm not entirely sure that I understand everything as well as I should, and I'm automatically skeptical of value fixing schemes since none has ever worked in all of history, at least so far.