yea, larger battle mods are essential. however i thought about reducing it. to how much however? 120? 150? also i soloed 11 invasion armadas at once with single nagato, more than half from beyond enemy range. however i do agree that small *** get annoying.
how about i increase its carrier slots? and have special frigate sized craft as an inbuilt escort? been toying with this idea for a while ngl.
11? ... now I'm wondering if I'm just bad at fighting, or if one of my mods makes the AI better at things.
Anyway, fair deployment/supply cost is a hard thing to tell... you could use Lunalib to give players modifiable options for the two big ones (Nagato and Pelagornis), you could also check other mods for ships in the same category for a comparison (Sunrider has it's titular ship going at around 90, I think, and I've found it about the same 'can solo fleets if used right' category. If with better speed/mobility and with fewer guns... the UAF mod also has some big ships). Though I'd at least consider 125 to 150 a good starting point, you can always fiddle with it later.
Giving Nagato more free carrier slots might start stepping on the Pelagornis's toes... though, you could give it fixed inbuilt slots. Put a customized 'Escort Frigate' (in the same midline style) in them that can't be swapped out and it's only job would be sitting around it hunting frigate to cruiser sized ships that get too close (prioritizing ones that are actively attacking maybe? Ship behaviour isn't something I know if you can mod). You'd have to make it so they can't be forced to engage away from the ship and only guard it, but I think that'd work. As for how many it'd need... that'd depend how strong you make these theoretical Escort Frigates.
PS: If you're getting back into modding in general, as opposed to just maintaining this one mod, you could look into making a Nexerelin 'Custom Start' option in the same vein as 'The Infernal Machine'. Where you start some kind of unique super prototype fusion of the Nagato and Pelagornis, but it's not complete and you upgrade it over time in the same way (using credits to remove otherwise un-removable D-Mods and reactivate systems/weapons or maybe by exploring for random schematics that you plant in the loot table). That could be pretty fun I think.