I've actually made a anti-metagame team myself. It's been working to great success. My best tip on making a team is to try to use pokemon that, rather than countering/walling to top threats, but can power through the top defensive cores. Without that core, many teams are very heavily weakend. Then finish the team off with a powerful sweeper. I have had huge success with this style.
EDIT: I guess I should throw in that CB Aggron rips defense apart. Just have someone else to take Steelix, Registeel, and Torterra, and let Head Smash destroy the rest. I've used mine with dual screen and sandstorm support to make him more thick.