I like...
Allows legal X-squadrons, keeps specialty cheese cut down, actually lets the ISC be more ISC, and increases base defenses...
Concern:
How do you tell which DNs of a 3xDN fleet are resupplying and which DNs are just sitting rock on a base/planet?
and a potential re-wording of a couple of rules for you, hopefully simplifying the work:
Capital ships are: all BCH, DN, & BB hulls, CVDs (16 or so fighter CA carriers), and CA-hulled X-ships.
Only one Mauler, Carrier, Capital and Fast ship per fleet. "Multi-Classed" ships, ie, those that fit 2 or more of the restrictred roles, count as the one allowed version of any/all roles it fills (so a BCV / BCS / CVA fills the Capital & carrier slots, Mauler DNs are capital & mauler, DNLs are capital & fast, DVLs are capital, fast, and carrier, etc.)
CA and CL X ships are not allowed to fly together. DDX ships can fly with one other X ship in a fleet.
Think about it for a moment. Currently, you define most capital ships, and state in a rule that they cannot fly together (so effectively one capital ship per fleet)
You have a second rule adding one more ship-type to the capital ship definition.
And the actual rule that defines an allowable fleet does not directly mention the capital ship restriction, but constantly infers it's existance.
All I do is combine all the capital ship definitions into one rule, and explicitly add capital ships to the one-of-each-type per fleet rule.