To be honest, it probably wouldn’t make much of a difference in the story. Dutch and Micah would’ve still been on the other side, and knowing Arthur, he probably would have let Javier go with John so he could fight the Pinkertons (and later Micah) by himself. I think Javier would be hesitant to go at first, like John, but in the end would take his friend’s advice. Javier might have been at Beecher’s Hope along with Charles and Uncle if he ran into John again.