How does one even begin to outfitting some of these ships? Sorta cheating by removing ammo on like, all ballistic weapons, but even so, these ships have some pretty tight fits in terms of spare OP.
I have custom loadouts on almost all of my ships. I tend to use a common combination of heavy maulers and light needlers. Just about every ship that's cruiser and up makes use of ITU, excepting missile-oriented ships like my Mercury as well as the Antares.
My Dakota uses a light needler on its forward mount, and a small broadside of two light assault guns on the right, with a vulcan cannon on the left. My Scythe varies, but it's generally an assault chaingun and two light autoguns or two light railguns, with a light machine gun on the forward turret. My Albatross uses four light autoguns, one light assault gun on the turret and an annihilator rocket launcher, with two vulcan cannons covering its engines (standard for all IF ships). Another variant I've been using (in light of a severe shortage of light autoguns, which are too good) I use two light dual autocannons and two light assault guns in the hardpoints, with a dual light machine gun in the front. This one's a little nicer.
My Toa uses two IR pulse lasers, two heavy maulers, four light autoguns, and a vulcan cannon. Alternatively, two light needlers on the hardpoints and two light machine guns on the forward turrets.
My defiant can use a similar loadout, though I prefer to make use of an assault chaingun+railgun combo instead. Riptide gives it the killing power it needs to compete with the Toa's 4 light autoguns and 2 pulse lasers.
My Shogun uses a one-two HVD and Mauler punch, with two light machine guns in its front turrets, and a single IR pulse laser in its energy mount for close-in assault potential.
My Vixen varies, but generally carries three Pilums and a heavy autocannon. You can give it a Pulse Laser if you wanna get ballsy, or even a heavy mauler, so long as it's something that allows it to fend off frigates.
My Montana uses a broadside loadout, making use of two heavy maulers, two light autoguns on the front turrets and two light assault guns on the right. Its left side has two flak cannons and a single vulcan cannon covering the engines. You can add more vulcan cannons to the right engine and front turret if you wish to give it more PD.
My Ares uses two heavy maulers and an HVD, with light needlers. My Yukon uses five heavy maulers and 8 light autoguns (light needlers work too.) My Antares is a single-sided ship with two HVDs and one mauler, with the standard locktide/riptide combo, and LMGs and vulcans on the right side.
TL;DR IF ships need to be as efficient as possible. My personal tactics dictate almost every ship must be a self-sustaining assault vessel, so I go for an HE/Kinetic one-two punch. They also make use of long range weapons where possible, where they can leverage their superior maneuverability. I always max out vents where I can, which is my default modus operandi with variants, unless it severely lacks flux capacity.
Hope that helped!
P.S. Light autoguns are seriously too good.