Hmm. I feel like this is assuming that "having weapons in all slots" is a good thing regardless of *why* there are weapons in all slots.
Because filling up mounts with guns on ships looks good. On the other hand, mostly unarmed ships look ugly, and it feels like an insult when such loadouts are more effective than one loaded with guns. It is certainly non-intuitive.
Unarmed Drover and Astral with high-end fighters work good, but looks stupid!
If I do not use (Sabot) missiles on Aurora, loadout is two heavy blasters and maybe some pd beams, rest of OP into flux and shields. Can win flux wars against other cruisers instead of losing by stalemate then PPT timeout because of insufficient flux trade advantage. Looks incredibly stupid.
Odyssey with two plasma cannons, two good fighters, and little else is a good build for the playership (has flux and shields to outgun just about anything); AI suicides with plasma drive, but beside the point. All those empty mounts, incredible eyesore. On the other hand, if I fill all the mounts and attempt double plasma, my Odyssey loses the slugfest against an enemy battleship due to poor stats.
I want to put big high-end guns on Onslaught like I can on Conquest, but that does not work, at least not since 0.8a. Instead, I need to be content with either SO-like loadout of HMG/chainguns (the Lucky build), or lots of needlers and missiles because dissipation is atrocious - yuck!
Mounts are meant to be filled with guns, not sacked for bonus OP, and it is a crying shame the game encourages that latter. The bonus OP excuse for mounts seems like a terrible cop-out. It was not that way with high-powered skills before v0.8a allowed most ships to fill every mount and kill things like they should.
(Related, in Diablo 2, I did not like helms like Vampire Gaze or Harlequin Crest [infamously called 'Shako'] on characters because they made them look hideously ugly, even if they were among the best items for various characters.)