I think that disabling communication trading is a great idea - I had no idea you could even do that. This could have a huge impact on the game, slowing tech trading, luxury trading, etc. It would open up new strategies - like preventing your hated enemies the Romans from having access to the scientific advances of the Babylonians...
Unfortunately, I don't think there's a way to be a middle man with luxuries. Historically, controlling trade routes was a way for an otherwise weak nation to become powerful (e.g., Venice). If you could trade/purchase extra luxuries from a civ, then you could resell them to other civs...etc etc. Now that I think about it, that would be a fun feature.
Anyway, I'm excited about this mod, and I think your idea is a great one - I may start a game tonight and disable communication trading just to see what happens.