make fleets require logistical support for long-term operation, even in the core, by making combat ships no longer function as light freighters & troop transports & tankers. A fleet of enforcers shouldn't be able to cross the stars on their own.
Every ship that isn't a freighter/transport/tanker gets a hullmod that reduces their crew, cargo and/or fuel capacity by 70/50/0/80%, every ship that isn't a cruiser gets an additional hullmod that reduces their c/c/f by a flat 20% additively with the previous malus (all military battleships get -100% logistics), and then any ship that isn't a civilian ship then gets the resulting logitical profile cut in half. The logistical hullmods that increase one of those stats gets the additional affect of negating that stat reductions for that hullmod's stat -- so your enforcer can carry enough fuel to go places, but it costs OP & a logistics slot to do it & will need another ship to house its crew or give up its second logistics slot to do it.
The reason cruisers dont get the debuff is that, well -- its in the name. Frigates & destroyers get it bc they're too small to house both battle armaments and a broad suite of logistical infrastructure, and battleships are large enough to house a broad suite of logistical infrastructure but use all of that space to house guns & armor instead. A cruiser, then, definitionally, is a ship large enough to house the logistical infrastructure to operate self-sufficiently and chooses that over battleship armament