I would agree with what you said about the stability of a wider tire, but there is only 1 drawback that I personally know of besides slight rubbing. I had 33x12.50x15's mounted on some Centerline 15x10 wheels on an 89 F-150 I had. They looked reeeeally sweet and handled good, EXcept for in the rain. WHen it rained hard, the wider tire wanted to try to float on top of the water in the road instead of cutting through it which in turn caused some nearly hydroplaning incidents.
On my Z, they 285's work great on the factory wheels. At a dealer in Tifton, Ga they set up alot of their trucks on the lot (04's) with 285/75/16 BFG All-Terrain KO's and 16x8 American Racing wheels which not only look bad-ass, the one I drove handled loads better than mine.
I have also seen only 1 truck that had 305 M/T Baja Claws on his factory wheels, he also had about a 6" lift though and to me it looked really nice. I still dont see how he avoided the tires scrubbing on the lower A-arm.
I would suggest, that if you want a wider tire, go with the 305's, which like you said have the height of a 285 w/ the width of a 33x12.5, and find some 10" wheels. Be sure you get the proper backspacing on the wheels as to avoid any harsh rubbing, but with the wider wheel, you will probably have to trim the lower air-dam a bit as well as crank the T bars a few turns (no more than 4), which shouldnt really mess up the geometry of the suspension, to keep the tires from rubbing the fender when turned fully to one side.
As for the K&N, I did notice a difference in throttle response, and a slight increase in gas mileage. I bought mine for $170 on e-bay, so I couldn't pass it up. I like having the re-useable filter b/c I live in the country where its reeeeal dusty during peanut season etc... It also looks better than factory to me, it intimidates some people
I hope I helped you out some, I might have not even come close to answering your question, but I will try again if you need me too!