Don't forget that even Episodes II & III featured R2 with rockets on his sides. Not that I'm defending it, haha. But the cartoons always adopt the more extravagant features to appeal to the younger crowds.
It goes to show how limited George's writing became, that he wrote himself into a corner, and the only way to get out was to give R2 rockets.
Everything else about this "Chopper" droid however seems pretty interesting, and a little humorous as well.