To my understanding, the Allies had not yet decided what to do with the High Seas Fleet when it was scuttled in Scapa Flow. What do people think of the idea of assigning the ships to the League of Nations as a peacekeeping force in an ATL where it's not scuttled? It would give the League some teeth, and solve the problem of what to do with the ships. Larger countries would be incentivized to provide crews in order to exert influence over the command structure of the fleet, and smaller countries could gain a cadre of trained sailors. Later, when the Washington Naval Treaty or an analogue occurs, ships can be gifted instead of scrapped. Imagine the Lion-class battlecruisers getting prolonged careers, USS Washington and IJN Tosa being completed and becoming LNS Washington and LNS Tosa. 
Perhaps the fleet could be based out of, and ostensibly protect, League Mandates. I would imagine that the ships would suffer from poor maintenance from lack of funding, but there's almost certainly many more ships than the League can crew, so they can be rotated through service. And anyway, if the League of Nations has any stick at all, even if it's not a big one, it drastically changes what it's capable of doing.
(If this idea is too far out there, it might do better in the ASB section, so feel free to move it)
Perhaps the fleet could be based out of, and ostensibly protect, League Mandates. I would imagine that the ships would suffer from poor maintenance from lack of funding, but there's almost certainly many more ships than the League can crew, so they can be rotated through service. And anyway, if the League of Nations has any stick at all, even if it's not a big one, it drastically changes what it's capable of doing.
(If this idea is too far out there, it might do better in the ASB section, so feel free to move it)