There already is a mod from back in the Vanilla days that extends the base game past the spaceship launch to include some SMAC based content. (Gets triggered after the spaceship launched) But to the best of my knowledge it's never been updated for G&K or BNW.
But if you want a different map from scratch, that's always going to be after winning a science victory in Civ V start a BE game. What's kind of new is that following winning a BE game via supremacy you can start a Civ V game with an advanced start to Information Era to personally take charge of the army you sent back to earth in BE.
(In SMAC, it was suffering a Transcendence defeat that tied back to Earth)