The Bothan spies weren't mentioned until Return of the Jedi, specifically in connection with the *second* Death Star. The Bothans had nothing to do with the first Death Star, the events of Andor, Rogue One, and A New Hope, as far as I can tell

I will be totally pissed off if they make him Gandalf, especially when the best story that can be told with the two Istar characters they've presented is that of the two blue wizards. I don't want to see a second age Gandalf and Saruman when they didn't arrive until the third age. I want to see the story of the only two wizards that did show up in the second age, and were in "the East", which would be Rhun. It's the only thing that makes any sense, logically, literary, and geographically.