MMO to Single Player

Build an MMO game the focuses on world building and gameplay for an MMO. Then once it's established. Create a quest path around a story arch. This story arch beta tests the story and potential gameplay. Refine it based on player feed back. Once considered good enough, build a single player version. You've already created all the assets, voice acting, audio, music, etc. due to it existing in the MMO. Also, the story arch with branching paths is created and refined. This significantly cuts down on work effort in creating a single player version. Just create the levels and refine the gameplay for single player. Sell the single player and capture the gamers that don't like playing MMOs.