It's a fine line you tread when you reimagine characters and stories in different kind of settings. If Superman: Red Son did not have nearly enough differences in it - being basically the exact same as any other Superman story and taking no advantage of the possibilities of its premise - then this particular story goes too far to the opposite end by having too much different.
Tony Stark's pulp incarnation is a Indiana Jones -esque gentleman adventurer, delving in ancient ruins and fighting Nazis. He's an adrenaline junkie rather than an alcoholic, and seems to be running away from his past and his father quite a bit more than in the main universe. He also doesn't appear to be overly concerned with weapons technology or arms manufacturing - it's all just sort of there, with very little story focus thrown at it - and more with starring in dime novels of his adventures.
Don't get me wrong, any of this could be made work: you could even preserve all of it and have just enough difference between him and Iron Man Prime to make the story worthwhile. If it weren't for the most damning thing of all: the armor.
Iron Man's armor is his Thing. It's what makes him special, sets him apart from all the other heroes and villains. Sure, you've got other power-armoured characters on both sides of the hero-villain fence, but Stark's armor is always the best, and the most tightly connected to the character himself. "The suit and I are one", as he himself has put it. Here, on the other hand? He suits up halfway through the story, Rhodey gets his War Machine armor right away, and then the Nazis go ahead and reveal their own mass-manufactured equivalents to immediately even the fight. The armour is at best a tangential part of the character and the story: it never seemed that important to him here, never had any spotlight, nor in any way special or more powerful or more impressive than the other suits. It was even first designed by his father rather than Tony himself.
The story is very low on personal stakes and growth: Tony is already an accomplished adventurer as we open it, he already got his heart injury (something that's never elaborated on either, though it's also an integral character trait), and overall it feels like him punching the Nazis is just another day at the job. Instead it focuses on this super-powerful metal trident that the villains could use to take over the world if they got their way. Yet I never felt it, because I never felt the characters. Pretty much everyone goes on about what a coward Tony really is, not brave enough to face the consequences of his childish adventure-play - but it's all telling and not at all showing, and even in the end I never got the impression that any of it stuck. He saves the day by blowing up more stuff, as he always did, afterwards seems ready for more of the same, and I'm not really even sure just what he was supposed to do to take responsibility instead.
Oh, and Pepper Potts is reduced to a damsel in distress. I guess at least part of it was because of the standards of the time period this is set in - written the way pulp stories of its age would have done it - but it could certainly have been done better and perhaps a little bit subversively, or at least give her more to do.
So on the whole, this one was a miss for me.