You can run 33 rubber on a stock jk, you may have to remove the plastic air dam thingy on the bumper. Lots of people do it with 16/17 rims, stock rims with spacers if it's 12.5 wide, or get the correct backs spacing. What's gonna be the issue is the 15 rim, they don't have a lot of room for the calliper to clear. Some fit some don't, even if you get one to fit the others may not, differences in manufacturing and tolerances for each rim.
I think finding that spacer 5- 4.5, is gonna be hard I don't see a lot of people trying to put 15 rubber on to the jk as the clearance issue scares them away. There are a few jk's running around with aftermarket 15 rims but most are going with 17 now, 18 are becoming somewhat easy to find rubber for as well.
If you have clearance issue and still want to run the rims, you can grind off some of the calipers to make room, not the best solution but it works.