I too would like to see all mounts being filled. But if they are not, it is not due to lacking for OP, but rather than there are much better uses for OP than another small weapon, or than for a mount with poor coverage. Once a ship has a certain amount of weapons, it has diminishing returns. A ship with 2 Plasma Cannons or 2 Gauss Cannons will not care much for an IR Pulse Laser for damage for another 5 OP. Perhaps there could be an argument in there to greatly increase the flux dissipation of all ships, but that 5OP will probably be used for something that isn't another weapon.
Yeah, it may not be another weapon, it will probably be vents so that player has even more dissipation, unless OP that can be spent on caps/vents gets slashed to half or more (and related hullmods removed). Then player might get weapons because he has the dissipation to use them (especially if flux stats go back to pre-0.8a skill levels). As for carriers, as long as fighters stay as missiles and cost OP and there are carrier hullmods, dedicated carriers will never have incentive to get proper guns. Fighters probably need to go back to being ships and decoupled from carrlers as in pre-0.8a releases for armed carriers (that can brawl and maul stuff) to happen again. However, with fleet slots, having enough fighters means not enough room for enough ships and no significant capacity to haul stuff.
For the rest...
Early in the game, when I use Shrike (P), I use whatever I find, which is probably (IR) pulse laser or mining blaster, light autocannon (because dual AC is surprisingly rare early, though not as much as railgun/light needler), maybe Ion Cannon, and Salamander (Sabot Pod is kind of rare too, often not available when I want it). By the time I have unlimited choice of weapons, I outgrow Shrikes, Enforcers, and Mules and use cruisers and bigger, plus few specialist ships. If I use Shrike (P) very late just to play around (in the sim), it will have a railgun and not either autocannon.
Efficiency Overhaul is not needed provided player has Fleet Logistics (a given due to how good it is for everything) and Navigation (mostly campaign QoL, less tugs means more slots for better ships). Without Navigation, I cannot haul a fleet about as big as NPCs can (multi-capitals) without burning too much fuel (bringing two or three Prometheus). With Navigation and fewer tugs, it is possible to bring a big fleet and wreck stuff like NPC fleets can.
I played games without Navigation, in an attempt to squeeze more skill points for combat (while I took colony skills before I knew of the Pather bug and other semi-hidden things about alpha cores and inspections). In the end, I get sick of burning too much fuel, then later, traveling from my colony to jump point, and crossing pulsar beams more times instead of T. Jumping directly to the planet where a pirate base constantly respawned at... and I took Navigation to remove two tugs and a Prometheus. I suppose if I remove Efficiency Overhaul from all of my combat ships, I can bring back the two tugs and Prometheus.
P.S. Back to Shrike, I might use single AC over dual depending what else it has. If it has Mining Blaster because that is all I have at hand (maybe Apogee just found a plasma cannon and the mining blaster it had goes to another ship...), I would use light AC over dual (if I have it) to help keep flux use down. More likely, I probably have multiple Shrike (P)s, and I do not have enough ideal weapons to arm them optimally.