It's a cargo hauling build that accounts for targets of opportunity, i.e. NPCs that spawn to try and stop you when you're running missions. I wouldn't put weapons on it otherwise.
99% of the interdictions will be in populated systems (the 1% will be when I'm not paying attention). The bounties are usually for factions in and around the system I'm working, meaning they are useful for building (and repairing) reputation and pushing influence. Combat is by no means the primary purpose of the build; the intent behind it - as mentioned earlier in the thread - was to annoy the NPC while I waited until the police showed up, then grab the bounty in a low effort way. As I noted there, however, the NPCs didn't usually last long enough: I was surprised by the combat capabilities. I don't usually fly Cobras for combat.
I could put a KWS on it, I guess, but I don't really see the point in that.
I usually put frags on my ships - I haven't done a laser/multicannon build in years, so in that respect it's an experiment.