How feasible is a Nexus 7 USB Mass Storage Case?

So I've had this idea sitting in my head for a couple days, and was wonderinf if anyone here thinks or knows if it is even possible. My gut is leaning towards impossible/implausible but I thought I'd share it anyway.

So it is essentially a case that you put your Nexus 7 in. I'm sure you've seen cases for phones that house batteries that you then connect to your phone's Micro USB port. My idea is more or less the same, however instead of a battery, it would contain a flash drive which would connect to the Nexus 7 via a USB plug built into the case. The case would of course be fairly rugged, as to reduce the likelihood of the flash drive being damaged. It could come in a variety of sizes, such as 8GB, 16Gb etc or even house a compartment that allows you to switch out sizes whilst keeping the same case.

Now I understand there would be some issues (if this is even possible). Of course the Nexus 7 doesn't have USB OTG Mass Storage device support stock, you have to root and modify some system files to enable this ability, which certainly reduces the market for such device. It also would mean you are unable to charge the device whilst it is in the case, which may be an issue for people.

It would definitely have its flaws but again I was just thinking of this the other day and was wondering if it's even possible?