Making an 'All Time List' for teams doesn't make much sense, for the reasons people mentioned on this thread.
I had rather have you separating them between eras, like you did for the duel lists. Sure, it's a lot of work, but only that way you can actually achieve a team list which is both relevant and coherent.
You wouldn't compare McEnroe and Federer even if they played each other in a few occasions, pretty much because they both belong to different eras of the professional tennis. With that being said, you can make an argument for one of them having played in a more challenging period and with proper reasoning and facts, pretty sure lots of people could get behind it.