Yes, Mon Mothma is a very minor character. Especially before the Andor show, which arguably gives her too much screentime anyway. General audiences wouldn’t freak out, they would say “who is she supposed to be?” You would have to develop her for a little while before you make it a big twist.

I’m not too familiar with the Yuuzhan Vong but I think that’s the kind of direction you have to go if you don’t want to repeat the Sith and the Empire again. Lucas’s idea of underworld criminal elements filling in the power vacuum left by the Empire is also good (though I’m iffy on it having Darth Maul.)