Lets see how it would work,
You pay me 1 BTC / per month to control 1000 BTC that I won't really give you (I just credit it to you). If the value of the BTC goes down. Buy back the 1000BTC and repay me the 1000 BTC. You reap the difference in the exchange. I never really risked anything.
IRL, I would give you the 1000BTC as a loan, if the value falls, you buy another 1000 BTC at the cheaper exchange, pay back the loan and keep the difference, (minus the fees).
Shorting is gambling, but a little better, it is gambling with OPM (other peoples money). And that is not done with anonymity, people want to know who's nose to bleed.
I already explained how I believe it could work in post #5 of this thread. Basically, you don't
lend them to me and let me sell them. You sell them for me (on the open market), while holding my dollars "hostage" and let me decide when to buy them back. This way you are simply gambling with your own money, since if you are wrong, the lender is still in full control and will force you to buy back the BTC if the exchange rate gets too high.
So you send me say $1000 dollars, and I don't give you the BTC. I just convert the BTC for you. Then you decide when you get to buy back the BTC that I didn't give you but will when you buy them back.
But I won't buy the BTC, ahead of time, I will just say I did. You will have the $1000 dollar credit, still. Then when you want to buy the BTC, I will then buy the BTC and give them to you.
I will do this for a fee of 1%, plus I get the interest on the $1000. Of course the fee will be consistent with the DTC (Days to Cover)
Your not really shorting anything, because I am just waiting for your next order before I take action. I will be shorting with you basically but I can't lose. I would even give you an ∞ DTC in case BTC doesn't fall for a 5% / mo
You would still make the difference profits cause I will pass that on to you for a zero sum, so from your point of view you won the bet. From my point of view, I say make another bet.
All the exchange would have to do is match your funds incase of an increase. In which case in reality, your short position is my PUT position. Either way I PUT it to you.