/u/mika6000 has a pretty cool rewrite of the story:
1) ChocoBros must go on a roadtrip for some sort of fun quest/mission for Regis (Not one for marriage). You're allowed to explore the world semi-openly (Maybe up to Duscae/The Disc) and return to Insomnia with success. Less fetch-and-return quests, more legitimate small journeys across what is already a large area. 2) ChocoBros experience the Insomnia invasion firsthand (As one of the earlier trailers indicated), they must escape but are forced to leave everything behind. Noctis watches his father die and the overall tone gets dark a la Versus XIII. With Cor's help they escape and manage to get beyond Duscae this time. Along the way Cor, Iris, and others become party members for extended periods of time though never permanent. 3) They rescue Luna, who joins the party for the rest of the game, and they battle their way back to Insomnia to take back everything again (With long quests along the way that focus on newer areas rather than Duscae/Leide, though those remain accessible and important). Original FFXV ending or alternate ending would both be fine (Though happy version preferred so you can come full circle to the beginning tone of game).
1) ChocoBros must go on a roadtrip for some sort of fun quest/mission for Regis (Not one for marriage). You're allowed to explore the world semi-openly (Maybe up to Duscae/The Disc) and return to Insomnia with success. Less fetch-and-return quests, more legitimate small journeys across what is already a large area.
2) ChocoBros experience the Insomnia invasion firsthand (As one of the earlier trailers indicated), they must escape but are forced to leave everything behind. Noctis watches his father die and the overall tone gets dark a la Versus XIII. With Cor's help they escape and manage to get beyond Duscae this time. Along the way Cor, Iris, and others become party members for extended periods of time though never permanent.
3) They rescue Luna, who joins the party for the rest of the game, and they battle their way back to Insomnia to take back everything again (With long quests along the way that focus on newer areas rather than Duscae/Leide, though those remain accessible and important). Original FFXV ending or alternate ending would both be fine (Though happy version preferred so you can come full circle to the beginning tone of game).