The armoured belt is manly for surface torpedoes.
The torpedoes won't hit on the surface- they will be set to hit below the waterline, where the armor does not protect. They will hit closer to the keel, and thus will completely circumvent the protection, turning it into a liability rather than an asset.
Aside from this, the engine rooms are not physically able to be located under the stacks.
The superstructure is too tall and heavy, and the hull is too short and stumpy.
The draft is insufficient, and the underwater hull is almost cartoonish at the screws and ruder.
That's my technical criticism... it also lacks the visual appeal that most royal yachts had.