The rules very all over the place so I don't know what they would be for coin like AUR. My guess is that it would be very hard to actually short AUR.
You have a some experience with shorting stocks, under one specific type of arrangement,where you have to borrow the stock, by way of a contract, and put up a margin.
What I am suggesting is very different.
1. We all deposit our AUR (as an example) with and exchange (or buy them there).
2.Some of these AUR are pooled into a hot wallet.
3. One player, the market maker, is allowed to sell those coins (our coins) on the promise he will buy them back.
It is not difficult as you suggest....but extremely easy for the market maker to short sell. He doesn't have to deal with all the red tape you have to when you short sell a stock. When you short sell a stock you have to deal with all the regulations from the lawmakers, and the loan provider, and the one who loans the stock.
Here under my scenario the market maker just has to have a deal with the exchange. A deal you are never informed about and which you don't know the details of. Possibly a deal against your best interest and that makes more money for the exchange at your expense.
You clearly have no idea what you are talking about. Also, I've have shorted a lot more than a stock or two, I once ended up short $250k worth of QQQ (before it was QQQQ) from some options that were exercised early. Many of my short positions were related to some form of option spread, most of which are far to complex to talk about here. (Multiple long and short positions)
1) There isn't any red tape or paperwork. It is simply a order gets filled or not. Margin requirements are setup in advance and loans are automatic at known rates.
2) Market makers actually have to follow the same rules, the advantage they have is access to cheaper capital if needed, know how much of an item is available for shorting and they are closely watching the order books (typically a higher level of data that is show to end users). They are also forced to take positions as that is their role in the market.
3) I'm pretty sure there aren't really any market makers in something as tiny as AUR.
4) If shorting in crypto coins happens it won't matter what kind of wallet the coins are in, that isn't a factor. It is a zero sum game.
The rules were things like a short position can't be started on a stock with less then a $5 price, etc. Very basic.
Of coarse most crypto exchanges are currently unregulated, but in general if they are going to be able to stay in business they are not going to be doing wild things. The most important measurement is if there is 100% reserve of coins. There is always scams out there like MtGox.