Is it possible to make separate books or stories in the style of FE3 or FE7 in FE8?
Fe7: Lyn mode and Eliwood’s mode, also you can use Hector mode through ASM.
I’d say find the prompt that gives you the choice between Eirika and Ephraim’s Routes, put the event before the prologue, and have two different maps/events for the prologue for which route was chosen, and have each game follow the tale (have the prologue send each route to a different chapter and never cross chapters unless you decide that 32mb of space is too little and you wanna be an eventing god)
If you’re talking about the save file changing colour based on who is the main character, you could just reskin the difficulty select to do that. Example mockup:
You can use the CHECK_HARD condition in your events to determine whether stuff happens in Eliwood or Hector mode, and you can either leave the hard mode bonus levels intact in the Chapter Data Editor if you want Hector mode to be harder or change them to 0 if you want it to just be different but not more difficult. Additionally, there’s a “make it hard mode” assembly hack floating around somewhere that you could use for a transition from one mode to another à la FE7 giving you the option to start from ch11 if you don’t want to play Lyn mode. The biggest hurdle would probably be some check to change which character can Seize/use the Supply command based on whether or not it’s hard mode.
All this being said, I would not recommend this to a beginner; all the conditions and checks you’d need to mess with are hardly worth cannibalizing the difficulty select. You might be able to use easy mode for a third book, but I don’t think there’s a CHECK_EASY event so the possibilities of what you could do with it would be very limited.
I’m pretty sure there’s a check for easy mode because there has to be some way that the tutorials are given