They seems like a good way to get rerolls for your 4 red dice, or for your black dice should it come to that. They are flexible, which is better than Ordnance Experts for Ackbar.
Are Gunnery Teams often put on Ackbar MC-30s? If so, is that second attack on a different ship better than rerolls on one attack?
I like the idea of Admonition with Caitken and Shollan, and Defiance being a gun line while Salvation finishes off escapees. It just gets expensive fast with the upgrades i want, and then light on effect squad cover.