I like the naval flanking move. This city is crucial, as it give us access to mounted units, which will be useful for open-ground warfare against their wandering stacks, so we can't be too careful. Do you think Sirius has landed a bigger stack somewhere in the north? I can understand saving their stack by moving it out of the city, but I thought they would use it to try and retake the city. It could also be that Slaze has decided to throw the weight of the Maverick forces behind Merlot. Don't forget we'll have to swing some galleons around the tip of the star to implement a blockade.
As for the Great Artist- I don't think CDZ will cave to any threats, whether they are overt or not. If we were to actually bomb them, they would see that as an act of war most likely, and would be at out throats as soon as possible. That is probably the case already, but this time they could definitely point to us as the aggressors. So I vote Golden Age. And, if it provokes a war, the bombing itself won't have been all that useful if we capture those cities by force, or lose the city we used to bomb.