You're lying if you've said you've never had a romantic dream about someone you've known as "just a friend".
It's human nature to flirt with the idea of being romantically involved with someone who is just a temporary infatuation.
As humans, we like to explore the realms of possibilities and pleasure without the actual commitment.
We tend to create scenarios in our mind in attempt to satisfy certain fantasies that we wish to happen, when in reality, wouldn't the best fix be to let them play out in real life?
What are you waiting for? You're one decision away from creating a completely different reality for yourself.