IIRC, he planned to take the dreadnoughts, the Radetzky- and Erzherzog-class predreadnoughts, the armoured cruisers SMS Sankt Georg and Kaiser Karl VI and all available Rapidkreuzer, perhaps even Aspern and Szegetvar. this operation would rival the bombardment of the Italian coast IOTL.
Regarding Oscarsborg/Blücher: the 28 cm guns in the norwegian fortress were of the same model as the guns of the Brandenburg-class.

