How stored belt armour might evade treaty limits

Could a treaty battleship be built for a 16-inch belt, carry thinner armour in peacetime, and receive stored plates in wartime?

It could be designed that way, but swapping thick one-piece belt plates would require advance manufacture and a major refit.

The hypothetical scheme treats belt armour as a 'fitted for but not with' treaty measure. The hull would be designed from the outset for roughly 16 inches of protection while carrying about 12 inches in peacetime. Thick belt plates are rolled to their final dimensions, so conversion would involve removing and replacing major plates; simply hanging extra thickness outside the existing belt would create difficult structural and weight problems. The full wartime plates would therefore have to be manufactured and stored in advance, turning the loophole into a substantial industrial and dockyard commitment.