In all honesty the people that we place in the "friend zone" usually have most the qualities we say we want in a mate. The primary reason we put them in the "friend zone" is because we were not physically attracted to them.
Generally speaking if you think someone is "hot" you are not going to risk blowing an opportunity to explore romantic possibilities.
Having said that just because when you saw them you didn't think she or he could be "the one" doesn't mean it's impossible to "notice" they have many of the qualities you're looking for in a mate. The problem is determining who put whom in the "friend zone". There is always a chance that (they) never had a romantic interest in you.
The reality is our mate or significant other has a better chance of also becoming our best friend rather than for our (platonic sibling like friendship) evolving into a passionate romance. Even if everything looks great on paper it's difficult to suddenly see a true bother/sister like "friend" becoming the love of one's life.