Thank you for your interest in my article! I appreciate it.
Your proposal, if I understand it correctly, is this: instead of market participants having to put real money in the system, and then being reimbursed if the bets are off (the naive randomization I and Hanson assumed), you propose that everyone can place unfunded orders at any time. If the bets are off, nothing happen, if they are on, everyone receives a bill for the full amount they ordered, all at once. Alternatively, everyone uses borrowed money to bet on margin, which is essentially the same thing.
You are correct that this does equalize the carry cost between the market manipulator insider and the arbitrageur outsider, which make it possible to profit off arbitrage that are small relative to 1/epsilon (but larger than the carry cost).
The main problem is that removing the requirement to secure the bets basically destroys the epistemic argument underpinning futarchy, which is that real money at play creates skin in the game forcing market participants to trade honestly. Under universal margin, no one has to trade real money to move this price. If the participants can default on their obligations to the platforms after the bets are executed, then skin in the game is largely fictional. If the platform requires some form of collateral, then capital requirements are back on the table.
The calculation in Appendix E is wrong. The Earth emits longwave radiation, which are at roughly the same wavelength as the emissions of the radiator itself. Per Kirchhoff’s law, the spectral emissivity equals the spectral absorptivity. Therefore, the correct heat flux due to Earth itself radiating is epsilon x F x sigma x T_earth^4, not alpha x F x sigma x T_earth^4. The contribution from reflected solar radiation due to Earth’s albedo is correct, however. The heat flux from infrared radiation from Earth is then 53W/m2 instead of the ~5W/m2 your model spits out. It reduces the net rejected power by about 8% in the 20C case, from 633 W/m2 to 585 W/m2. Not enough to change the overall argument, but having the correct physics is always good.