I actually don't know which weapon would actually help at all for a Squid. In close range I would probably prefer a front/starboard bifecta, so the rear guns wouldn't be used. For anything further than that, the only time the squid's back is turned to the enemy is when it's fleeing, but then again the rear gun is usually not repaired so it would be useless anyway. That's pretty much the only reason why I'm considering the mine launcher.
Other options I'm weighing presently are Artemis (easy and fuss free, plus nice damage per shot) and Banshee (easiest way to burn the enemy while fleeing), but as mentioned I doubt they would be used at all.