If a holder of a private, commercial, or ATP pilot certificate operates an ultralight aircraft; and that aircraft is also equipped with the radios and transponders required by an airspace for GA aircraft, can this flight operate under standard VFR rules as a GA aircraft rather than operating under ultralight rules? (ie. Using non-towered airports which are marked "ultralights prohibited" in the chart supplement, and controlled airspace airports.)
All of the regulation of airspace that I can find is focused on either the pilot's certificate and rating, or the aircraft equipment, rather than the aircraft category and class. That is a slow "experimental" light-sport STOL bush plane (which could be as slow as an ultralight), a C172, or a King Air 250 are all equally allowed into class E, D, C, or B airports as long as they have the required electronics and a PIC with a private pilot certificate or above.
I ask mainly because I would like to use an ultralight for commuting, and the places I commute are airports of the above nature. (local street traffic is terrible, and I need STOL capability for my home field. Less than 700ft to clear a 50ft obstacle.)