My argument against building it on the first turn is that you want to leave open the possibility of Sealion to force UK to build defensively. I like 1DD, 1FTR, 1BMR because these units are all useful no matter what Germany decides to do. The DD clears out the Russian sub from SZ125 and pays for itself even if Germany doesn’t buy any more navy the entire game.
I also don’t think messing with Turkey or the Black Sea are good for Germany. The neutral crush slows the Axis’ momentum too much. For a German naval strategy, I think that only Sealion and Afrikacorps are viable. If you aren’t going to dump a bunch of IPC’s in the water and take London, the only real naval play I see for Germany is to build just enough out of Southern France to tip the scales in the Med and move into Egypt and the Middle East.
What I like the Romania major for is for pumping out inf and art against Russia, either on offense or on defense. It could also help deter an Allied beachhead in Greece.
If you’re going for a rapid advance and taking Moscow as soon as possible, I don’t think the major in Romania would help because you’d rather have those 30 IPC’s in the form of units on the first turn and then you’re going to build fast moving units on subsequent turns where the proximity to the front doesn’t change anything that much. You’ll also have Ukraine and Volgograd earlier. If plans change and you need to dig in, I might consider buying minors for Western Ukraine and Rostov. I’ve never done that before but I think it would be more helpful than having that Romania factory.
In any other Germany strategy besides the fast Russia push, I agree that the Romania major is a good buy. I just wouldn’t do it on turn 1.