It's starting to take shape.
If Alex Reyes makes the opening-day roster, it will be as a reliever. Shildt shared that today. Now, there is still a chance Reyes could shift from the bullpen to the rotation during the season, but that would be tough, especially for a pitcher who is going to be monitored as closely, health-wise, as Reyes.
Carlos Martinez is going to have a conversation with the team this week about his return and role. It has not yet been decided if his gears will be switched to reliever, but that is still a possibility, one I believe is getting stronger every day he goes without pitching.
Hudson and Gant are battling for the rotation spot Martinez's setback opened. The one who does not win that competition could go to the bullpen too, though you're going to have to have some starting depth at Class AAA Memphis.
Think about having these arms in the bullpen: Martinez, Reyes, Hicks, Miller, Gant/Hudson.