You make it sound like that would take a mere few hours to do.Add 4 little cut scenes in the game. And call them chapters. Have the game load at each chapter if a player wants to - for NTR and Loyalty paths. You now made it extremely easy to see content without the gallery and to switch between paths faster at specific points of the game.
I do like the chapter idea and if we were starting from scratch, that'd be a nice way to do it. But there's simply to much code that would need to be pulled apart and re-created.