Sorry if this has been mentioned before but I couldn't stop my urge for posting after having read the first four pages.

In principle I'd be interested in the slim back cover version, but I have a suggestion for it:
As we all know the stock back cover is not flat because the camera is protruding about two millimeters. Long time ago I've been thinking that if one would have made the back cover flat a full-sized SD card might fit between standard battery and back cover. And with a very flat adapter it might be possible to connect an SD card sitting there to the microSD port.
If one can afford the bigger format full-sized SD cards only have advantages over microSD cards. They are cheaper, faster, have more storage capacity and hit the market earlier.
Of course as an all-thumber I'd still need someone else to build this tiny adapter for me. But I'd be optimistic to find someone if there were some drafts available.