Mount cerbs instead of mortar, but I highly doubt that the IMG battlecruiser will be any efficient in PvP against similar or higher opponents. Also, either go for full solaris, or full cruiser turrets. Don't mix up those.
I find 2 Missiles ( One faction and one basic if possible ), 2 Razors, 2 Prims, Flak, and rest Cruiser Turrets very good in battle. I've used it on the Bullhead and LABC, not to sure about the IMG one and KNF.
If bombers are a problem, all you will mostly need is a flak and razors, flak to deflect Novas ( if the bombers are Nova spammers ), and Razors to insta kill them.
When using Razors against snubs, mostly when they are trailing behind you, hit reverse into them and catch them by surprise, usually works, or catch them EKing for decades. Hope that helped ))
Cerbs, and regular cruiser turrets. This is the most multiporpouse setup for caps.
I'd recomend pulse turrets for light cruisers, which has ony 2 heavy weapon slots, however, BC should have enough slots for heavy weaps, so save regular slots for simple cruiser guns.