Mining investments are based on calculations of future difficulty. In a sense the miner is short difficulty. The miner would be able to hedge that exposure away by buying such a contract, locking in his profit.
Well, understand those are just calculations, in the same sense that a gold prospector would estimate the amount of gold he could extract from a mine before he started mining. You can't hedge that risk away because it is inherent to the mining process. You can remove all sorts of risks to your profits that aren't actually related to mining (such as the price of gold, exchange rates, labor and material costs, etc.) with various forms of futures contracts. You can even hedge away the risk of various unforeseeable things like an earthquake messing up your mine, with insurance. What you can't do is hedge away the risk that you simply miscalculated the amount of gold you would mine and thus end up with less than expected. Bitcoin is pretty much the same in this regard.
Incidentally, most miners do not have any profit to lock in (and if they do have an expected profit, it is rare for an unusually high difficulty increase to wipe that out). Using those same calculations that you mentioned, we can see that most mining products on the market today mine at a loss. The uncertainly, and hence possibility of profit, is what drives people to buy in the first place. To see this, imagine a hypothetical scenario. Imagine I have setup a mining pool\cloud mining site. I will sell you 1Th/s on my site for 3 months, "lock" the difficulty at it's current rate, and implement a PPS model. So you know, with absolute certainty, that it will generate 2.691BTC for you (assume for the sake of argument that you know it isn't a scam and I won't just run off with the money). You can easily see that there is no way I would sell this contract to you for LESS than 2.691BTC, and there is no reason for you to purchase it for MORE than 2.691BTC, and hence this product will never exist.
The interesting thing is that this is precisely what ASIC manufacturers do when they sell ASICS (though I do not believe that is the primary reason WHY they sell ASICS). If you make or buy say, 1000 ASICS you are "betting" the difficulty rate will go up lower than expected, or at least not higher than expected. Selling some of those miners for a fixed rate of BTC now, today, partially offsets that risk. Leasing the equipment for a fixed rate of return also has this effect.
