adywan said:

I've figured out a way of Obi-wan having a pupil that has turned to the dark side and that's why Yoda is reluctant for him to train Anakin.

If you have ever addressed this directly then I apologise, however, this suggests you are planning to keep Yoda in the prequels. It would be a shame to go to all the trouble of keeping the Anakin/Vader surprise, and not even consider keeping the crazy green muppet/most powerful jedi master surprise.

Sure a lot of existing footage would require a lot of work to remove Yoda completely, but maybe send Liam Neeson an early copy of ESB:R or something with a persuasive note suggesting you may need him to film a few new scenes.