I'm not sure about the 3% increase part...never thought about it in those terms. However, the larger the tires, the lower the gearing needed to keep the drivetrain happy. That being said, there's a sort of buffer zone you can play with depending on what you're using it for. So usually, 33" tires go well with a 4.10 gear ratio and keep things in the driveline about what stock would be like. There are several gear ratio calculators out there but I like the one on GrimJeeper.com the best. Take a look at that and play around a bit. That should get ya started on gears and tire combos.
Another thing to think about is the increase in rotational inertia from larger tires. Obviously, bigger tires weigh more. So when it comes to stopping, we might require more force to stop than stock brakes can handle. On a 2012, you won't have that issue as much. Older models like my CJ-7, that really needed an upgrade.
Another thing with the added weight to consider is the impact damage created when you're out wheelin. The axle shafts are not indestructible. A few hard smacks while out doin hard rock crawling and you might snap an axle. It happens. A lot of guys tend to either reinforce the axle housing by having it "sleeved" and then also reinforcing the C bushing (bushing? Is that what it's called? Can't remember...haven't had coffee yet) or they replace the stock shaft with chromoly shafts or they do both. This way, when you get the bigger tires that let you play on tougher trails, you're not slamming away at the steering/driveline system and getting stuck when you break something in the middle of nowhere.
Hope all that helped!