I now have pretty often seen a Gat/Flamer/Artemis Junker. I dont know about that one, you need a special way of approaching (other than gat/flak) which may be hard for new players. Furthermore you need a good co-captain to win with this setup. Also it highly depends on your enemies.
I figured out a way to use a Galleon effectively, been using it since... a long time. You need to know the basics of how to pilot a Galleon though (move as less as possible, stay at one position, only turn your sides with the enemy).
It contains 2 far range guns on the left side as well as a mercury and 2 CQC guns on the right side. Rear gun is a carronade.
That way you can shoot them from fair away and if they get close - simply turn your right side. If they get behind you and you cant aim for them (although using claw/kerosene) just shoot them down with the carronade, gives you time to repair and reposition.
I don't know about the all banshee squid... you don't have piercing guns on there and the banshee doesnt do that much damage.