A stored cruiser hull still needs machinery and crews

Could old armoured cruisers be hidden as coal-service ships with their guns stored nearby?

Possibly, but idle hulls would be difficult to maintain and reactivate after twenty years, especially without trained crews.

A few old armoured cruisers might be presented as coal-service ships while their guns were stored separately. That disguise reduces their visibility without keeping the vessels ready for war. Machinery deteriorates unless it is maintained, and a trained crew cannot be conjured when mobilisation begins. The proposal shows the difference between possessing a hull and preserving a usable naval capability.