What a 28,000-ton British battlecruiser specification implied

Could Britain build a 28,000-ton, 29-knot battlecruiser with ten 14-inch guns and a 12-inch belt in 1912?

Probably, but meeting the full specification would likely push the ship above 28,000 tons.

The proposed 28,000-ton specification was difficult but within the broad competence of Vickers in 1912. The combination of 29 knots, ten 14-inch guns, sixteen 6-inch secondaries, and a 12-inch belt places severe competing demands on displacement. A British yard could attempt the design, but the finished ship would probably exceed the exact tonnage. The complete requirement must be judged as a system rather than as a list of individually plausible features.