If no WNT, just build G3s and improved Arks Royal.
Within a treaty environment?
To get a full length flight deck on Courageous, Glorious and Furious, would hull blisters/bulges forward be required to fit a full-length flight deck, as the ships apparently lacked the structural strength otherwise? If so, I think it would be worth it, even with a drop in speed from 32 to 30kn. Then, rebuild Furious to this standard with a proper island. Hermes is the most modern of the rest, so she can be a proto Light Fleet Carrier. Eagle should be sold/given incomplete back to Chile.
I would also suggest retaining Tiger instead of the Iron Dukes so there would at least be a third active battlecruiser when Hood gets her "large repair".
When it comes time to build the KGVs, it's pretty obvious that nobody else wants to drop to 14". Even if you aren't going to go to 16", at least build the 15" Mk. II for their use.
Somehow get an earlier Hunt type escort destroyer, and get the Dominions building them as well. Put them in the escort role, and if not already building, have a ready-to-go design for a minesweeper that can be built by civilian shipyards. More standardization on the fast destroyer types too; more Tribals and less "Letter" class emergency boats
Either expand the testing tank at Denny's or build a larger one at one of HM Dockyards. Adopt welding too, the KGVs would thus expend less of their weight in rivets.