The Montford Point landing platform is essentially a cut down supertanker ( the predecessors of today’s Ultra Large Crude-oil Carriers, ULCC) which can ballast down and ‘lean’ so hovercraft can come aboard in open sea. One option is to similarly use this type of craft or similarly modified commercial hulls as cheap almost disposable carriers as needed. A sub divided double hull tanker is very hard to sink and the hull plates are sufficient to keep out small arms and splinters. Plus armoring and fire fighting kits are available and cheap today. The ‘fighting’ bit’ would essentially be a mod kit (a skin) that can be updated, moved around, even stored ready for war, the hull could be almost any commercial large bulk carrier. Heck large container ships are very fast today as are some RoRos, so you don’t even lose much strategic deployment speed.