Kallus requires you to pick at the start of the first round, and that choice is locked in for the whole game. You can't repick round after round.

This is true, but even given that I don't think it's going to be too difficult to identify the priority target in most lists.

The bigger problem is, I think, going to be that Kallus will paint a great big target on whatever ship he is on.

Kallus + Rebel Captive

On Kenkirk, along with the Moff. Once Kallus' target is gone, chuck him out the airlock.