Since Utah was able to summon herself as a shipgirl and proved herself in combat, the cat is out of the bag. I think that every nation, both Allied and Axis, will now be trying to summon their own shipgirls for use in combat. I think that the British and the Americans will have the initial advantage in regard to summoning shipgirls. Although I am not sure if the British and the Americans will collaborate with the Soviets in regard to potential shipgirl summoning project.
Well the problem is that while Utah self-summoned, with wartime censorship and the slow and limited speed of data transmission, the news about exactly what happened at Pearl will take time to percolate, and proof that the wild story is real will take longer. Now the US Navy knows, and can be presumed to share the information with the Royal Navy (who have proof that shipgirls exist in their steel hulls). There's also a very strong cultural bias against women in combat if there are viable alternatives (and in this case there will be viable alternatives like those in OTL). This also does not count the cultural and theological implications of ships having souls.
For the Japanese, this is a bit trickier, since while they will be culturally more predisposed to believe that Zuikaku has a
kami on board, Tanaka is a junior pilot in a very hierarchical organization that he would have to persuade. Also it will be a while before they lose many ships going off OTL events, so it would be even longer before they look to try to resummon the sunk (probably after Midway would be the earliest they even start looking into it). A further problem might be if the summoners have to have proximity to the wreck to summon, remember Utah summoned on her sunk hull. Rather tough for Japan then.
I think that Schreiber may encourage the German shipgirl program for a number of reasons. He needs military support for any future coup and summoned shipgirls will be very useful in that. Also, he may think of having summoned shipgirls in order to get enough military force to get a negotiated peace. He does not want the Soviet Union to conquer Germany as it in the OTL. Although I may be wrong and he may just try to summon shipgirls secretly.
Who is he going to summon apart from a lot of U-boats and possibly a few destroyers? Well the
Panzershiffe like Graf Spee perhaps. Gneisenau's already summoned and int he UK and Bismark, Scharnhorst and the CAs are unsunk and accounted for. Unless the ritual would allow Bismark's spirit to leave her hull, it's of limited value to him.
P.S. does Schreiber have the loyalty of all shipgirls in the Kriegsmarine? He has the loyalty of most of the surface ships but I am not sure about the U-Boats and the others? Where would the loyalty of the other shipgirls lie? I would imagine that the newer shipgirls maybe more loyal to Hitler and Germany.
You don't get much newer than Bismark right now until Tirpitz is built. As for the U-boats, that's a good question, I'd think Schreiber would be a possibility or Dornitz with the caveat that some of them might be ardent Nazis if their captain and crew were fanatical. Generally speaking the KM was pretty much more pro-Germany than pro-Nazi though.
Regardless of anyone else, we know he sees at least Zuikaku.
I'd presume that now he can see them, assuming that he's in a position to see them, IE walking through the mess hall on Akagi.
It's the IJN brass, do you think they have the competence to actually listen?
Admiral Yamamoto was reasonably competent, and some like Admiral Tanaka were very good. Now whether or not they will listen to someone that far down the chain of command is a different story, he would have to persuade his air group commander and captain that he's really seeing Zuikaku and not gone mad as the minimum first step.
