Perhaps a module that takes a lot of space which allows a ship to share its total Life Support range with all other ships in a fleet with it. If it has no weapons and decent armor, it will be the last ship that enemies try to kill, therefore, a Carrier is a completely viable idea.
More than just allowing carriers, this allows true 'support' ships, rather like refuel/rearm ships in a naval task force. It sounds very logical to me that space fleets should have supply ships that allow them to extend their range beyond what their internal stores provide.
Going further, perhaps a component that allows its speed rating to be used for all the other ships in the fleet. Another essential for the 'carrier' concept, but also an interesting conceptual ship that would create some sort of 'warp bubble' to help transport an entire fleet.
Now, the balancing... First, these ships will have a pretty high logistics score. Secondly, these components will take up a lot of space. Meaning, that second component that allows a ship's speed to be used for its entire fleet, would disallow it mouning five or six engines and being ridiculously fast; it might mount two or three at most if it foregoes defenses altogether
So why then would players use this tactic? Late in the game, you could make very viable Tiny and Small ships by forgoing engines and life support and just mounting tons of armor and weapons (or just weapons). But, right now this is more of a defensive tactic and a desperate one at that, who wants to wait ages for a bunch of little ships that'll die fairly fast to get to the combat theater? With a carrier, they can be transported at good speed and at long range.
Logically, all other ships in the task force would want to escort their carrier / supply ship so it doesn't make sense for the carriers to get killed first. Thankfully, it would also be nonsensical in the current design for enemy ships to go after the carriers first. Especially if they're using a non-cargo hull, and they're loaded with armor, they're the LAST target the enemy would go after.. they don't want to hammer away at this armored barge while fightercraft are raking them with withering fire. It becomes viable to lead the entire taskforce, carrier and fighters, into battle. edit: Just want to point out I just noticed the poster above me said pretty much what I said just not as longwindedly. Sorry.