Divergent Paths: The 3 Scenarios

The solution on the Ghost leaving the party came to me very quickly, and thanks to some great shorthand coding of the following events (There was no check for party membership for Shadow's remaining scenes, nor on Gau's for the Nikeah ferry. The game just listed both of them as "Party Character 2"), I mostly completed the 2 brothers' scenario tonight. I just need to figure out a quick, elegant way to prevent the character from accessing Barren Falls until the scenario is done.

Couldn't you put an NPC guarding the falls and have them say something like "The Falls have been closed off for some reason or Edgar and Sabin are like "I don't think this is a good idea right now" or "We shouldn't be here, let's get out of here" something like that. It will at least make it logical.