Your idea has potential but you don't have an way to get your characters from point A to point B. This is what most writers call being blocked. I hate the term "Writers Block" but if it works for you fine.
The problem your facing is not that you don't have any options, it's that you have too many. What? Am I crazy? No, other wise your would have stopped reading. You have an endless world of possibilities. So many directions that you are forced to stay still.
What you need to do is write yourself in a corner. There is nothing like a complete lack of options to force you to get creative. Once you have nowhere to go then the unexpected happens.
If you your have characters reach there arch too soon, IE: the guy gets the girl, have the girl have a shady past as a call girl. Or have have her inherit a million dollars. Something needs to toss the viewer for a loop.
Why do they care about your story? What are you trying to say? Don't be flexible with the theme but be flexible with the story. You will surprise your self and once you get really into your own story and characters. That's when your there. When you want to know what is going to happen to your own characters that is when other will be hooked as well. But, this will never happen if you don't go anywhere. Force your character in impossible situations they will surprise you as you surprise yourself.