I just had an idea for a calamity effect. I think Diplomacy would be the civcard to give the effect, but maybe one can think of another one.
It would make it possible to avoid Barbarians or parts of them by bribing them with tokens from the treasury or commodity cards. It would cost, say, 2 points of value per unit. And for a larger amount, maybe 5 points of value/unit, one would be able to use those very barbarians as mercenaries and lead them to invade a bordering enemy, controlling the way they go.

MMM.... intereting! I like it... now let me see how I'm going to work something like that in.

Something like that would probably make the Kushan happy because they are vulnerable to Barbarians, but have no sea zones to burn treasury on.