Personally I wouldn't recommend mixing roles in a single build because a ship will only perform partially as well as a dedicated build. That's my personal preference but I respect other peoples play styles. Different strokes and all that.
There are some good recommendations here. I'm disappointed but not surprised that shock canons weren't mentioned. Shock canons get overlooked because of their very low ammo capacity. But its my understanding that the OP intends to defend their ship from interdictions rather than hitting up a local RES or CZ with this build. Shock canons are perfect for this kind of limited engagement. They absolutely melt shields and chew through hulls. For a while I ran 3 large on my mission running Python, nothing else. It ruined everything except for the SCB spamming T-10s but those are easy enough to run from.
Besides ammo capacity, other drawbacks to shock canons are that they can produce quite a bit of heat if the distributor is drained. Also they don't have auto fire. But pulling the trigger for each shot is worth their destructive potential, even a bit satisfying if you ask me.
My recommendation would to be for 2 in the large slots, engineer one of the beam lasers with thermal vent experimental to offset any heat issues. Alternately you could go with 2 mediums and put them on the hardpoints over the nacelles. I recommend gimballed but turreted could be interesting on the nacelle placement and could make fire group assignment easier.
Since the OP seems interested in packhounds, my final recommendation would be to engineer them for rapid fire just for the full Macross experience. Its kind of hilarious but a potential drop in frame rates might be a possibility. Just depends on how many launchers are equipped and how fast they are fired.
OP, I hope you have fun with your build. Please update here when you finalize it and let the rest of us know how it works for you.
Big ol edit: Going back through this thread looking for ideas for theory crafting I see that I overlooked Vedmo mentioning shock canons. o7 Cmdr. Glad to see I'm not alone in my appreciation for them.