In Monado Archives, there is a small addendum on page 226 that talks about a prototype story for XB1. It comes up in my conversations with others a lot, so I wanted to translate it here for easy reference. There is a translation project for XB1 in the works by the way, and you can check that out/help them out on their discord server here.
“In Iwata Asks, there was a comment of an early plot where a certain character close to the game betrays the party, and this comment was discussed at length in the community after the interview was published. Asking Takahashi and Takeda, they said it was a very early storyline that went something like this: after Reyn loses Sharla, he tries to go back in time to change the future. However, they find out, were they to do this, it would result in even more lives being lost, and Shulk opposes this. In the end, Shulk uses the Bionis’ power, and Reyn gains the Mechonis’ power, and they battle it out to decide who gets to decide the future. As you can see, this is quite different from the storyline we got. Asked why this wasn’t used, Takahashi: ‘it would be sad for a friend that was with you the whole journey to betray you at the very end.’”
Also, earlier in the book in the interview section:
(Talking about favorite characters)
Takeda: My favorite character is Reyn. Especially because in the beginning, there was a time when we were trying to set the two of them (Shulk and Reyn) on opposite sides of the spectrum and go for a buddy film type story. We ended up doing a story about Shulk and Fiora though.
Mira 
Talk about Reyn time
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