[X] Build a coastal battleship
As a member of the battleship mafia I was obligated to vote for this right out the gate.
But there area a number of practicalities to consider. For one, those pointing out that battleships are not the future are correct. The carrier will indeed obsolete the battleship,
about 15 years from now. At the moment, there are exactly
2 aircraft carriers in the entire world. HMS Argus, and HMS Furious. (The latter of whom was placed under refit to have her central tower and superstructure removed and replaced with an entirely flattop flight deck
last month) USS Langley and
Hōshō are currently under construction. The only carrier aircraft in British service I've yet to find (At least the only one not listed as "Spotter/Reconnaissance" if there's a bomber I missed that's active in 1921 please let me know) is the Gloster Nightjar. A fighter whose armaments consist of 2 fixed forward firing .303 Vickers machine guns. Carriers are in their
infancy and any war fought on the sea for the near future will be fought and won by battleships.
And that's putting aside that the only enemies we're likely to fight at the moment are Poland and maybe the Soviets. Both of whom are in the Baltic, a sea which has never been especially kind to carriers of any sort. Since just about every part of it is within range of land bases and thus can be swarmed by enormous amounts of land-based planes.
I also find the idea of Trade Protection laughable. From what bases? The Empire is lost, and all the German overseas bases with it. Germany can't reach anywhere that isn't it's backyard. The only powers that could threaten our trade and wouldn't also completely roll over us are Poland and maybe Sweden. Neither of whom would be overly impressed with 2 cruisers alone.
Not to mention any early 1920s cruisers are
also likely to be obsolete by the time carriers are in ascendancy as well.
That having been said I was under the impression the British wanted a semi-strong German Navy in the Baltic to act as a counterweight to the Soviet Navy? How harsh are the naval restrictions anyway?