Regarding the calibre of this new ship.
I can understand the rational for wanting the heaviest guns possible but it really is a big push to get them into a ship of this required displacement.
If the calibre drops you can get more wiggle room for a better balanced ship. At some point someone will point out that a 12" gun, whilst not able to match a 15" or 16" in raw power is still able to severely damage most capital ships. Yes it wont win a fight against any Battle line ship but it can mission kill them by damaging vital equipment and has the advantage of placing limits on the Germans.
At some point someone will have to lay it out that you cant have a ship that does it all on the displacement available, their will have to be sacrifices. Designing a ship to a purpose, even if it is a secondary purpose is more likely to produce a useful and adaptable design than trying to design an adaptable ship to strict limits.
Is like practically trying to build another invincible all over again, but with the further disadvantaged that there are already ships that are able to hunt her and sink her with a scratch.
I just had a thought, correct me if I'm wrong. IIRC, the Germans can't put any new guns on their capital ships. The smallest British caliber at the moment is 13.5" or 34.3cm. German calibers at the moment are 12"/30.5cm and 13.8"/35cm, which is larger than the British 34.3cm gun, making it illegal. As long as the Germans aren't allowed to mount a new gun on their ships for the duration of the treaty, that means they are effectively limited to 12".
Yes, that's correct.