The Beatles's greatest contributions to rock actually come in the production and advertising of albums. They were the first to record the music and vocals as well as any additional background music, like a string section, seperately and mix them together later. Before, it all had to be done at one time. They also pioneered music videos. Since they were in so much demand for TV programs world-wide, they made these little films set to their music to send out to shows they could not attend.
As far as a reunion, I know that John and Paul had been considering it after Lorne Michaels of SNL made the running joke of having them reunite on his show to the extent of having George Harrison on. I think it would have worked. Just one night where they play everyone's favorite tunes, and they go back to their respective careers afterwards would have been perfect. Look at the Simon & Garfunkle reunion in Central Park back in the early 80's. It was one night of the two of them just jammin' out their old tunes to a shitload of fans. After the show, they went their own way. The show neither bolstered or hurt either man's career. They were in the same situations as they were when they came in.
