This. Which is why I'm grateful that it sounds like Sharon's getting introduced in TWS, for now. Build her character first, see where she goes. If the story dictates in Cap 3 that she and Steve find their way toward each other, and it's organic to their stories, then good, have them get together.
If the story also dictates that they stay colleagues/friends/partners, then that's fine too.
I think Marvel and the Russos get that Sharon shouldn't just be thrown at Steve, considering he's still dealing with losing Peggy, adjusting to the modern day, etc. While Sharon's role may be smaller than some would like, it sounds like she'll get her turn at kicking butt in TWS and at least start developing as her own character and not simply a love interest for Steve.
I'm still not entirely sure BW will be Steve's love interest in this movie either. But I do love that she and Cap will share the movie in a big way. I actually wouldn't mind not having a conventional love story in Cap. For me, he's still dealing with his unresolved feelings for Peggy; I say give the guy a break in the romance department LOL!
I wish more people asked ScarJo and the Russos about any connections BW and Winter Soldier have in the past and if that's something that will carry over from the comics to the movies.