Skimama

My 2015 AWD Ford Edge sport 2.7l v6 is rated to tow only 2000lbs with the 20" rims being the reason it is not 3500 like other edges. If I change my rims to a smaller size not normally offered on the sport, will I be able to increase my towing capacity or is there more to it? I am wondering if there is a gear ratio aspect as well because the only thing that is referenced in the towing chart footnotes is the rim size.