So, dating several women from one family is okay as long as you keep updating to a newer, prettier model?
Anyway, that's not even my main concern. I'm more troubled by the coincidence of Cap running into, and falling in love with a fairly close relative of his first love after almost 70 years. That strikes me as the kind of silly, convoluted plot-twist that comics are sometimes guilty of, but shouldn't be encouraged in the movie adaptations. Of course, sometimes that sort of thing can't be avoided. For examble, I was fine with Peter Parker's flat mate's father being the main villain, since Norman Osborn is a significant character in Spidey-comics and the connection between Pete and Norman was actually interesting. But does Peggy Carter really have a huge fan-base that would be sorely disappointed if their favorite isn't in the movie?
I don't know if the first movie really needs a love-interest that's involved in the action. Not to mention that there's no reason they couldn't give Gail a more active role. Or for that matter, keep Peggy but give her a different surname and thus avoid the unlikely Carter family connection and its questionable similarities to a sub-plot from "Austin Powers".