I think a Super Star Destroyer is too big to look right to scale to the size of an X-Wing Raider.
But! What about something the size of the Resurgence class from Ep. 9, at the size of an X-Wing Gozanti/GR-75? It would still be nice and gigantic (being twice the length of an ImpStar), but fit better mechanically on a 6x3 table, because a base the size of the Raider/CR-90 would have major problems with it's yaw making the rear of the base sweep ships aside.