Better?? If they are perfect!!! I don't think they need anything to improve. we al know they imporved on their own, JOHN and Paul were always trying to imporve their songwriting, their instrumentation, everything. Also their manager, Brian, was always trying to improve things for them.
George was a hell of a guittarrist and Ringo could play the drum marvellously (have you heard him in "Rain" and "Strawberry Fields"? Amazing!!