Your frame is too outcome dependent. If you can't do pickup and you only have one option, then you are going to be in a monogamous relationship whether you like it or not. Furthermore, it is unlikely that a girl from a traditional background is going to be okay with a friends with benefits relationship. She may go along with it for a few weeks (to see if she can change you), but not a year and a half.
There are other issues as well. If you are new to pickup / relationship game, then you are going to have a difficult time maintaining a strong frame for a friends with benefits relationships. Here are the community accepted rules for maintaining a long-term friends with benefits relationship (
http://puarticles.blogspot.com/2008/01/ ... rules.html ). One of them is to only see the other person once a week (twice at the most). It doesn't sound like that's going to be an option for you.
Your situation is not ideal.
-Wolf