There was one experimental single seat Avenger. A rather crude job wit the turret removed and a 'fairing' replacing it and another one covering the lower gun position. Fprward armament was increase to three .50 cal guns. Speed increased less than 10mph.
The idea is NOT a good one. The bulk of the size and drag of an aircraft does not go away if you simply remove gun mounts/positions from an existing airframe. The Avenger had more square footage of wing area than an A-20. It was roughly 66% bigger than a P-47 wing. Almost 20% more wing than a Skyraider. It was roughly 500lbs heavier empty with a smaller, lighter engine than a P-47 and sticking a 2000hp engine in it is still going to leave it slow. Maybe a 6% increase in speed on top of whatever you get from better streamlining?
Enclosed bomb bays add speed and range to planes that have to go a fair distance ( carrier strike) BEFORE dropping the bombs. They add weight and bulk to short range aircraft, like tactical support. They limit top speed AFTER the bombs are dropped.
Avengers worked in the Pacific ( or had to be used) because the Japanese didn't have very good AA and they were available on the carriers. Using them in Europe against a much more numerous AA defense is going to result in higher losses.