Thanks for clearing it up, Germany might have been justified in that. But generally how effective would auxiliary cruisers had been if they had been if the ships had built from the ground up with the latest weapons at that time?
Much more effective, but building them from the ground up would greatly raise tensions with the UK and cause an naval race. And this naval race will eliminate the advantage of custom designs. IOTL, a German AMC was able to sink a British cruiser, so the design of OTL is quite effective. Just as the submarines of the 1939-1941 era were effective. The biggest bang for the buck is better codes which is effectively free, and might even save money. Often using off the shelf equipment is cheaper than custom modifying for military usage. There are also the related issue of poor communication procedures and training. The Germans knew/suspected their codes were broken in the middle of WW1, so this is really an open secret. Second, you want more of them, even if the design is less effective. So these things need to be spammed out just like the U-boats. And just like the U-boats, you have to be willing to take casualties. If 90% of AMC crews die/capture in the war, that is just war.
So lets jump to writing an ATL where I want to buff AMC and want to minimize the chance that negative butterflies (i.e. UK reacts strongly) actually nerfs the AMC. What do we do? And let's try to avoid absurd foreknowledge like France will quickly fall but Hitler will throw away the win by attacking Russia and/or the USA entering the war.
- Planning. We need good quality staff work by staff level officers in the 1920's and/or 1930's. We need them to do things like keep detail list of German ships convertible to AMC. We need them to have list of what is required in terms of weapons, men, material, and shipyards. This is doable by probably under 20 men, so we can easily hide it in some civilian naval agency. Or hide it in some retired admirals estate. We are talking about a single floor of a single building in Berlin with paperwork. And maybe some of the more sensitive paperwork hidden in mine/basement somewhere. Keeping a list of German flagged merchant ships should not alarm the British. Neither should having specs on most of these ships. These can be in your maritime safety/regulation agency. The thing you hide is the list of what is needed to convert the ships.
- Supplies. This probably has to wait on Hitler openly rearming. We need to stockpile things like naval cannons of about 5" or so. Stockpile machine guns. Maybe even stockpile some conversion items. If the planning is done correctly, then we may have identified things such as shortages of some welding materials, etc. Fix where possible. The UK is generally assumes German has been doing these two things since 1905 or earlier.
- Enigma. Germany in WW1 had coastal boats (torpedo boats, mine laying ships, converted fishing boats) using the same code book as U-boats. The pattern of the UK operating around the harbor protection minefields tipped off the Germans the codes were compromised. They just did not do anything about it in WW1. It is not hard logically to know that you will lose AMC and lose the code books and machines. So it is not hard to figure out that these ships should operate with separate coding systems from the rest of the armed forces including the rest of the Navy. Also not hard to figure out that you don't want these things chatty since radio triangulation worked in WW1 on both land and sea. You either buy the better Engima machines or even better yet, use one-time pads.
- Production. We are probably not going to have a 100 + sea planes sitting around for adding to these ships. So we need to work on the production lines for supplies that are not stockpileable. This one has risk of UK detection and counter measures prewar.
- We have no idea what year the war starts, so we will likely get caught off guard.
So Hitler invades Poland. About a week after the war starts, we activate the plan and start spamming out these things. Probably can do about 5 times OTL rate or better, at least for first year or two of war. Limited effectiveness since so hard to get around UK before May 1940. We can send a big size convoy 5-20 via the Arctic Sea to the Pacific in the summer of 1940 instead of just a few. The we have the military definition of luck. Luck is where training/planning hits opportunity. We get lucky, France falls. We can then mass covert the merchant ships in French ports and send them out. And we can keep sneaking ships around the UK that can come back to France for repairs. If I write the ATL where we custom design merchant ships in the 1930's to be mass converted to AMC, I will likely trigger a British response. Some of the things like putting a lot of extra steel in the hull in places needed to support naval guns is a dead give away. As would be putting cranes on merchant ships combine with a deck area to hold a couple of planes.
I have spent a lot of time on ship design between 1905 and 1930. There is a reason ships fall into easily identifiable categories such as AMC, CVL, CL, CA, etc. When people do compromise/hybrid ships, the designs suck. They under perform and over perform on costs. If you want warships to be merchant raiders, you build the panzerschiffes. 20+ of these will cause the British Admiralty fits. The British need the traditional warships to defeat the IJN such as CA and CL. To defeat PS, you need to build faster ships with bigger guns. The closest design in IOTL is battlecruisers, but this is overkill. The British need to build a bunch of 13" gunned super fast ships. Call the BCL, or light battle cruisers. Putting these gun/engines on a ship combined with long range means things like very limited to no torpedo protection and maybe light armor. These ships will cost a lot,but actually be worse in a naval battle versus IJN CA. And will be one hit, one kill ships against IJN subs and mines. And there cost will be much closer to a BB than CA. You can look at the lengthy criticism of the Alaska class to understand why. If you want AMC, you get free hulls and very cheap ships. The cost is the guns, the labor to convert, and the airplane. Almost free compared to a PS, so you don't have to worry about losing them. If I try to compromise the design, I get this odd ship that is part PS and has cargo holds. Probably cost what a PS does but has less performance than an light cruiser.
Hope this helps. My main point is that without foreknowledge, we probably make most of the mistakes the British and German Admiralty does. We would just have a chance to adapt faster and not take 30 failures to learn, only 10. Patton was a good commander cause his troops got better. If you take his units performance in 1942 in North Africa and have his 1944 breakout of Normandy units perform the same way, the breakout is a fiasco. Same idea here. Germans can learn faster, and Germans can start learning earlier.
Hope this helps