It's no more difficult to re-gear a 2012 than a 2011, the issue is with recalibrating the computer, and that is solved with the recent up grade of the ProCal.
The only problem with 255/80R17's - aka 33x10's - is that they are available only in load range E, at least as far as I know. Your JKU doesn't need or want load range E tires, D's are more than sufficient. But a set of KM2's would be a great tires, if a bit stiff...
I would still run the spacers. My wife's JKUR has the original oem M/T's and I put a set of specers on her Jeep to get the tires out from under the fenders. Looks much better with the tire sidewalks out to the width of the fenders.
Photo, hers = Rescue Green Rubicon on oem 255/75R17's, aka 10x32's, T/A KM M/T's, mine = white Rubicon on 12.5x37's:
JPK