What does this do for post-war German naval construction? ITTL the HSF can claim they went out and fought and died and while they may have "lost" in a strict tactical sense, their loss helped bring about an earlier end to the war on terms fairly favorable to Germany.
Probably gives them some leverage.
Since the treaty limits the German navy to 1/2 the tonnage of the Royal Navy, there will be definite limits on post war German construction, especially if Britain decides to retire all of its 12' gun BBs and BCs (something that might be considered in a peace-time environment even absent a broader naval reduction treaty akin to OTLs Washington Treaty).
Assuming that, Britain's fleet in 1918 would comprise
21 battleships (5
Warspites and 5
"R"s, together with 11 older 13.5" ships nearing the end of the usefulness). Given the fact that Germany's BC fleet was essentially eliminated at Jutland, I could see Britain scrapping the majority of its own wartime BCs and completing the
Renown and
Hood classes -
perhaps six BCs, with the 1921 BCs being in development (I'm presuming the
Glorious CV conversions).
Using the estimates of a RN with 21 active battleships (10 with 15" guns) and 6 planned or soon to be active BCs (all with 15" guns"), Germany would already be at, or nearing treaty limits:
10-11 battleships and
3 battlecruisers. New ships could be constructed only by scrapping existing ships. Of the German BBs, only the 15" gunned
Baden class could be considered modern (let's assume all 4 are completed), although the surviving
Konigs might still be useful for a while (I'm assuming one or two may have survived the Jutland debacle). Probably Germany would be better of scrapping all the remaining obsolescent and obsolete 12" and 11" gunned BBs, so that leaves maybe 4-5 ships of a new class. It would be interesting to see Germany go the fast battleship route for these. Regarding BCs, the situation is clearer.
Hindenburg (the only BC not at Jutland) and two
Mackensens.
Regarding the British
Glorious class, if they are converted into CVs as in OTL, this would allow Germany to follow suit. Possibly
Hindenburg (relatively undergunned) might be converted to a CV, and an incomplete
Mackensen might also be considered as well.
All this is presuming that Britain in 1918 does not try to match the US and Japan in their own naval race, seeing neither nation as a direct threat at the moment (Japan is still technically an ally and the US is a "friendly" non-aligned nation). Later, after the Anglo-Japanese alliance lapses, my TL presumes that the UK seeks a diplomatic "understanding" with the US equivalent to a non-aggression pact, so penny-pinching Conservative Party governments only need to stay ahead of Germany.