Hi JanJan, welcome to the forums.
For some of the logistics skills like Makeshift Equipment (percentage maintenance cost reduction), Containment Procedures (percentage fuel cost reduction) and the leadership skills, I've got two thoughts:
Option 1: think it would be pretty convenient if those could be hullmods, or better yet built-in hullmods like salvage gantry's; there's already the Ox-class tug that gives a fleet-wide bonus to speed, so a dedicated logistics hull ship that affects things like that could be neat.
I'd point that those skill effects already are in hullmod form on a per ship basis. The Efficiency Overhaul hullmod does both. And indirectly in the form of Expanded Cargo holds and Auxiliary Fuel Tanks (needing only 1 logistic ship instead of two because of more capacity also saves resources). A built-in hullmod for global less supplies is mostly a reskin of Salvage Gantry already. One decreases how much you spend, while the other increases how many you earn. I feel like there isn't a need for both since at the end of the day, after you've spent a month salvaging or fighting, you'd be at the same amount of supplies with either method.
A hullmod that makes a logistic ship into a better Ox, i.e. more speed for less fuel, seems like it would obsolete the Ox itself, which seems not ideal. Also, I'm guessing Alex intends the high fuel cost and ship slot of the Ox to offset the benefit of higher fleet speed. Otherwise everyone would be running around with 10 of the things.
In general, if you're moving global campaign skills to logistic ships, and one wants to keep the same level of difficulty, that means reducing the maximum number of skills. So if all the leadership skills are just ship slots, then the player only gets 5 or 10 skill points to keep the same difficulty curve. Also, since ship slots and credits are much available than skill points right now, a player would typically include all these logistic ships in every fleet, no? Would you be decreasing the ship slots along with these changes? Down to something like 15 or 10? Or would every player fleet simply include 1 of each of these leadership replacing logistic ships, since there are not any significant downsides? I'd worry some variety in fleet builds would disappear.
And a larger salvage-rig-like logistics vessel (a dedicated fleet tender vessel perhaps) that has a built-in hullmod which reduces your maintenance costs by a percentage, with hull-size and stacking considerations taken into account in the calculations.
In some sense, Salvage Rigs can be viewed as reducing your net cost by finding more supplies in per fight and per exploration, and naturally scales with fight size. A global supply reduction, which is based off a logistics ship, while thematic, I think overlaps a bit too much with the currently existing Salvage Rig concept. It would have to be like the Ox or Salvage rig, bringing little but it's global bonus. And it would be presumably designed to work only for large fleets, because any global percentage discount that was worthwhile in small fleets would be excessive for a large one for the effort involved. Basically every end game fleet would have to have one or more, or else you're being inefficient.
Option 2: Logistics officers and Bridge Staff. Essentially officers you can have in your fleet who can pick those skills or variants of those skills, letting you spec into other things. Not sure if they should be part of the existing officer limit or have a different count though.
To summarise, moving those "affects your entire fleet tremendously and only you can do it" skills and de-centralizing them, so that if you still want those you have to invest in it somewhere else, freeing up your character to be the unkillable super god-warrior with all elite combat skills you dreamed of without being annoyed remembering your other character's Wish.com-tier maintenance costs.
Mechanically, what do you see as the difference between using a limited set of points to pick certain pictures on the skill screen to get certain permanent bonuses, and having a limited pool of bridge officer slots, and picking a picture on the bridge officer hiring screen to get certain permanent bonuses? Isn't this just a different way of splitting skill points into personal and fleet pools, and reducing the ability to swap points between them? So would you have like 8 bridge slots and limit the player to 7 combat skills, to maintain the same level of difficulty?
The suggestion of sharing these bridge slots with the current officer pool I haven't seen before. I have heard the suggestion of having an officer be the ship captain instead of the player, and using said officer ship bonuses, but converting an officer slot to a fleet wide bonus is new to me. Not sure how it would work out. Probably would depend on stacking effects and how strong the individual effects were. I need to think about the ramifications more.
I've looked at seeing if I can do Option 1 through modding (by looking at MakeshiftEquipment.java, and DriveFieldStabilizer.java to figure out how a hullmod affects campaign layer stuff), and so far the api seems like it might work, but I'm curious to see if there are any changes to the officer system before I throw myself into fiddling with it.
I'd look at the Efficiency Overhaul hullmod for the equivalent of Makeshift Equipment and Containment Procedures, for a ship specific version. As for global bonuses, yeah looking at the skills themselves is probably the way to go.