Is there a design for a "slow, armored carrier"?
If your main battle line is a set of 21 knot ships, can you build a set of "slow" CVs to work with the line in the late 1930s?
My initial thoughts would be, build the CVs small and cheap like destroyer escorts. If I go the other direction I build the slow CV capital ship sized, but armor it up?
Springsharp seems to suggest that an armored CV of the Illustrious class needed ~150-200 tons of ship dedicated to support an aircraft in the simulator.
This seems to suggest the following characteristics for a "slow CV".
1. 7" of deck armor
2. 4.5" hull armor
3. 23 knot speed
4. ~60 aircraft in hanger. Maximum compliment ~75 aircraft including deck.
5. 35,000 standard ton displacement
To me this seems roughly viable. The Illustrious class was ~2/3 the size, and 7 knots faster, with half the aircraft capacity. Add displacement and remove speed, room should be made for a 2nd complete hanger deck and supporting equipment for aircraft. The Eagle was roughly as big, and carried roughly as many aircraft, was 8 knots faster, but with significantly less armor. Any slow CV design would likely place a premium on catapult take off operations.
End result should be a CV that can handle a hit by a ~1600 lb dive bomber, a 2000 lb skip or mast height bomber, or a torpedo with a 750 lb warhead just as well as a BB. No faster than a slow BB, but able to keep up and undertake flight operations with the typical BB cruising speed of ~14-16 knots, and far more than enough to stay in position to a merchant or invasion convoy. Not the kind of ship that would be of any use in style of the fast moving, slashing attacks typified by the allied side in the early part of the Pacific War. Maybe something that would be useful in escorting convoys in the Mediterranean? Or in escorting amphibious invasion fleets and slow BBs on the allied side in the later part of the Pacific War, or possibly the Japanese side of the early Pacific War?