Has anyone tried going for bigger tires in the rear and making the rear wheels an inch smaller to match the front?

I am aware it's difficult to find many options for aftermarket wheels on the xfire. I haven't really be able to find anything I like yet. I was thinking if I go for thicker sidewalls on the rear tires to fit 18" rims but keep the same overall outer tire size as the orginal 19" wheels, then that may open up some possibilities.

Is this the ramblings of a mad man or could this actually work?