Think of all the "very large" aircraft carriers that have been built in the last 15 years

If you scoff at the concept of building battleships and battlecruisers of over 100,000 tons displacement, think about both the number and size of large nuclear powered aircraft carriers that have been built for the US Navy. They are nominally 1,092 feet long and about 97,000 tons full load. They can make 30 knots or so, as well. The largest warships completed in 1945-1946 were the Midway class aircraft carriers, which were approaching 1,000 feet in length. Their displacement was fairly low, but not as low as the nominal 45,000 tons. CV-42, the Franklin D. Roosevelt was about 67,000 tons. If the decision had been made to go very large, the capability existed to do so. Also consider that the destroyers were on the verge of going very large in 1945, as well. The Mitscher class are an example.