I like the idea, too! I never had more than 3 experiences players to try this, although we did discuss possible mechanisms of teaming. For example, the two players in a team use their own colours and everything else works the same as the standard rule; you just add the final scores of the two in the team.
Before I digress too much

Owning two base games is definitely a direct way to owning 14 meeples, but I suppose people could just play mega-carcassonne with more meeples in teams. Sounds goods?
What order do players take? Red 1, Blue 1, Red 2, and then Blue 2? Would Red1-Blue1-Blue2-Red2 work? This order might makes it easier to trap meeples. After all, 14 meeples sound a lot and I think we should add some mechanisms to make it more challenging.