I have a map of the Star Wars galaxy that I got in a Star Wars Insider years ago. If the story that is being planned requires a new planet just ask and I will pick one that best fits. Also, regarding the Jedi Temple I think it should be on Caamas. Caamas is right beside Couruscant and on the map I have it says the planet was destroyed 19 years before the Battle of Yavin. This is timeframe that the Jedi were destroyed in ROTS. You could put the Jedi Temple on this planet, and have the newly formed empire destroy the planet resulting in a mass obliteration of the Jedi. Yoda wouldn't be on the planet at the time because he would be on Dagobah, and Obi-Wan could be off planet hunting Anakin.