I can definitely see how it slots together in some ways—like you said, there's little clues, and I do remember seeing confirmation that this had been long in the works—but it reads like a retcon to me. The presentation is what threw me, I think, and it makes it hard to shake that "thrown together" feeling. It might have been better for the story if they had done it right away, since that might have saved us from needing pages of "and this is what happened". :\

Oh, I never expected any real presence from present-time Tony, not with the way his story is going. Even though Reborn seems to step out of continuity, that would have been too much by far. But all we've gotten is three mentions/appearances, when as far as we know Cap's last memories would be of the tag end of his and Tony's Epic Break-Up. Granted, mostly the flashbacks seem to have covered Cap's distant past so far, so there's still time for a couple more mentions. Maybe it's just part of the over-all pointlessness of Cap's drift through time. (Though I do have hope for something there after what happened in issue 3.)

I had not heard about Siege, and it's a huge relief! \o/ I was twitching in fear that they might end up setting Tony aside to deal with Iron Man Without Tony Stark or something similar. Thank you for giving me the heads-up! ♥