Scott Pyle's Goalsystem engine delivers on all points, with Supersystem 4E or Blasters & Bulkheads or some combination of the two probably being the easiest to make fit. You'll have to accept a relatively low level of detail/differentiation (ie SS4 vehicles work very much like "regular" supers) but there isn't much those rules can't do.
Alternate choice would be Shock Force/GWAR, if you can find a copy of one or the other. Little light on the "RPG lite" element, assuming that means character advancement.