Hypothetical villain Mon Mothma as a Robespierre or Stalin-type figure might work better than her having always been an imperial spy. It doesn’t undo the ROTJ victory and would contend with the reconstruction of revolution in an interesting way. The paranoia of imperial conspiracy leading to an extreme crackdown on counterrevolutionary activity, demagoguery for the sans-culottes, and maybe some dark side bullshit for good measure. It would be a fine line since you’d have to try not to indict the whole movement the OT is predicated on, but having our heroes struggle with their allies’ descent and questions of what a galactic government post-Empire would actually look like, feels the most like a natural progression to me. It synthesizes with the prequels too.