I think there is certainly a chance depending on how spots open up. I assume they will want to add 1 SP in free agency to Wheeler, Nola, and Suarez just to have depth, and then have the other spot be a competition between Falter, McGarry, Abel, Painter, and who ever else is still around. From there it depends on injuries and effectiveness. They are certainly getting McGarry, Abel, and Painter into a place where they can step in if there is space and need.
I don't know if there is a list of things that Painter needs to work on, as much as for him and the other two, a lot of what they need is facing better hitters. How are do they react and use their pitches when guys are chasing less or able to match up to the velocity a bit more. I think Abel and McGarry have a bit more to work on with nibbling less and getting outs in the zone, while I think Painter could use some starts where another team kind of punches him in the mouth and forces him to really battle with the full arsenal.