It's definitely an interesting proposition, but a Germany that goes gung-ho for the UK needs to think about some careful diplomatic moves in Europe - it can (probably, assuming it can build the dockyards in time) a competitive navy with the RN if it can either:
- both focus it's production on ships, and limit the UK's production and ensure the UK doesn't have any navally strong allies;
- focus it's production on ships, and enlist other allies with strong navies to dilute the RN focussed on Germany.
Britain (not counting Canada, which was also handy for naval construction) produced more than twice as much tonnage as Germany during WW2, as well as more (and, on average, larger) aircraft, and while Germany handily out-produced the UK in tanks, they didn't produce so many tanks that if they shift all that production to ships they can out-produce (or even come close to parity) in terms of naval production with the UK, if HoI is even marginally historically plausible.
The biggest potential pitfalls for Germany are a US, French or Italian alliance. The US out-produced the rest of the world combined in naval production, so whoever they line up with is likely to win any naval confrontation over the long term, so the first priority is keeping the US out of the game, followed by enlisting either Italy or France (or preferably both) and then making sure the USSR isn't going to come knocking when all you've got to defend the Reich with is a handful of divisions and a whopping great fleet
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Yeah, though even with Atlantic ports Germany's navy would still be limited somewhat. Ideally, you'd want bases further afield than that, though to some extent you can make up for that if you can get Japan into the war as soon as possible. Getting to a position of beating the RN in a straight up fight in the North Sea is not really feasible. But if you can threaten the Empire, then you can force the RN to redeploy and weaken itself locally. This was really the issue the Kaiserliche Marine had - despite all their power, they had no way of projecting that power anywhere useful (and in some ways, a big part of why Germany was Britians "rival" in the early 20th century - the latter chose a "rival" that wasn't really a threat to them).
Sounds like early-20th century Britain would have been a good EU4 player
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to an extent i disagree with your presumption that you cant supply an invasion force on a beach head or from port, the best example of this is Normandy were they supplied the entire operation until the broke out of the hedgerows from artificial "mulberry" harbors. And as to unloading divisons to support the assault it would depend on Size of elements + ships and available landing scraft. 30 divisions in an hour is a little preposterous but over the course of a day, i could see that if not more.
Thirty in a day is still a huge amount. D-Day and Husky were both around 7 divisions in a day, and while they both reinforced quickly afterwards, upwards of 30 a day is far, far beyond anything anyone on this planet has accomplished ever. This is with a stupendous amount of landing craft, landing ships and preparation as well. I'm not saying people should be limited to 'just' a D-Day sized assault, but anything larger should require a huge effort (as opposed to HoI1/2/3, where you could drop 10 divisions off (and pick them up again) almost as easily as going out for pizza!)
