Going back to before the season started, they expected JD to play some OF (he started 35 games in OF last year) and either he or Arroyo was going to play RF against lefty pitchers. Everything seemed fine with Arroyo playing OF in spring training.
It's not accurate to say that they planned on Bradley playing RF every day. That specifically was not the plan as of April.
Arroyo started 16 games in RF, all but one before the end of June.
But JD's barely been able to run all season, and Arroyo couldn't make the transition to OF. If either had worked out, then Bradley would have had fewer at-bats, and more times coming in as a defensive replacement.
Neither of those worked out at all, but they were actual options that were part of the OF picture before the season. Add them to the list of things that blew up.
Another OF backup plan in place before the season, in case Bradley couldn't bounce back, JD couldn't play the field, Duran didn't hit, Franchy didn't hit, and
Arroyo couldn't handle OF, was to have Refsnyder, vet RH outfielder, stashed in AAA. As it turned out, that one actually worked great. Until Refsnyder got hurt and missed a bunch of games.