Dominion battlecruisers as dry-dock policy

What happens if the Royal Navy scales the F3 battlecruiser design to 42,000 tons for Dominion flagships?

It produces a heavily armed flagship and leverages prestige and treaty obligations to secure major dry-dock investment across the Dominions.

The counterfactual enlarges the F3 design from roughly 34,000 to 42,000 tons and uses the extra displacement for a very heavy 15-inch battery. One flagship for Canada, Australia, New Zealand, South Africa, or India would advertise each Dominion's treaty-recognized status. More importantly, making the ship as long as possible would require its owner to construct a correspondingly large dry dock. Prestige and treaty obligations could secure infrastructure spending that a direct request from the Royal Navy might not obtain. The result expands imperial repair and basing capacity as well as adding five capital ships.