Hello Dorknought,
First, I am not Riain, I'm taking ideas from Riain and Dr. Alexander Clarke and combining them into a what if.
Second, the proposed operation is one to be conducted in 1915, not in 1918 with all the pressures therein. Mutiny is a real risk, but the situations would be unique to both, and is not a guaranteed thing.
Third, the reality of Germany not having enough slipways is a good point, however, a standardisation on a class of very similar vessels, ie a Blücher style of ship, should be cheaper, and faster to build en masse, and whenever they feel like they have too many of these ships, they can choose to build more screens instead, just as the British can choose to build more of a counter to their choice.
Fourth, the Armoured Cruiser threat is sure to be countered, however, how it is countered is not clear. For example, the British might expect these Armoured Cruisers to be used in commerce raiding missions past the Dover Strait and up the North Sea, maybe even into the Atlantic (doubtful), and decide the Battlecruiser concept, being able to maintain the same speed, but with greater gun range and armour, would be a sufficient counter, rather than simply building more of their own Armoured Cruisers. In this case, the British are not likely to benefit, a Battlecruiser at these ranges is just as vulnerable as the Armoured Cruisers.
Fifth, my understanding of torpedos, submarines is that these technologies are not really operationally reliable in 1915, the RN cannot in fact just "bring in large numbers in both Destroyers and the largest submarine fleet in the world". Being charitable, Germany will have their own screening vessels, their own torpedos, etc, rather than simply producing only Blüchers with the 900M Mark budget they'll have.
Sixth, your remark at the end, I find it without point to alternate history. The RN exists, it stops any Naval Invasion, it will always stop any Naval Invasion, therefore history could only be the way it was, no matter what you try to do. Then, respectfully, if you believe this, why are you even on this forum to begin with? If you don't believe this, why bring it up?