Comments on the 15" guns. I keep saying that it was an overengineered gun with pretty unimpressive characteristics for its caliber, even in 1914. The new 14"/45 had about the same performance, so reducing Lion main armament does not make any sense - rather a revised KGV design with 3-4 quad 14" turrets. OTOH there's a lot of time to finish the necessary 18+ 16" guns - or just buy them from the US if gun making capacity is that critical.

Also keep in mind that the Russians have the Sovietskiy Soyuz and Sovietskaya Ukraina very close to completion, and another 2 Kronshtadt class BCs (launched sometimes in 1941), and the other two BBs might not get canceled with the POD. So one more reason to get 16" gunned ships.