Adding pre-crisis Darkseid or any other version of Darkseid to the Godhead is gonna do absolutely nothing, basically like adding a complementary pea-shooter to an Eclipse SSD.
Also unless the writers are braindead and didn't understand Final Crisis deeply, but Godhead Darkseid is entirely outside the effects of crises and most retcons. Whenever Darkseid or Fourth World itself were affected in cosmic events like COIE, Zero Hour, Potentially in OWaW had Imperiex succeeded, or Infinite Crisis, what was effected were actually merely the emanations/avatars (avatar isn't a correct term for Darkseid) of the Godhead and the Godsphere.