Originally Posted by The Question
He's an Iron Man villain who has a backstory that lends itself to having him either be The Mandarin's minion or a third party working against both Iron Man and The Mandarin. I don't see why he shouldn't be in the movie. He can always be redesigned for the film, and his powers aren't really that bad. He's super strong and does energy blasts. If his powers are lame then so are two of Superman's.
As for the name: If you're playing up the spy background, then the femininity of his name doesn't matter. Code names aren't meant to sound badass or masculine. They're simply meant to be what's written in the official reports and what's said over communications so the other guys don't know who your man is. The Unicorn sounds like a classic espionage code name from old 60s spy thrillers. And while in the U.S., Unicorns are often associated with stuff like My Little Pony, there's nothing wussy about them. They are symbols of strength and purity in folklore.
And, in a slight digression, they are also often symbols of femininity, but not in a weak or unimpressive way. When they are feminine symbols, they are symbols of feminine strength.
1. Putting in a third party would crowd the movie too much, remember Spider-man 3?
2. There are more interesting villains that could work as henchmen, with better non outdated backstories and cooler powers
3. a guy doesn't want to be a symbol "feminine strength", a guy shouldn't want to be a symbol of feminine anything!