Seems like from your story idea that every person will be THE Hero. For a MMO you really can't have a story thats based on a single hero and have every person be that hero. For a MMO you need a story involving many heros and let the players be those heros.

For example have the story be about a Army and let the players be the members of that army.

Also 6 months may not be realistic depending on what your aiming to release with the first Alpha Test. What features do you want to be complete at the first Alpha test? Depending on the size of your team my best suggestion is to aim to have a Authentication system in place and then the ability to move around and chat with other players online. Maybe a few buildings, trees, ect scattered around the place to make it more interesting.

PM me if you would like help with programming! My engine could be ready for a first alpha test like I am describing in about 3 months instead of 6 months!