I don't know whether Columbus would do it, but 2 young guys that stick out as really attractive targets if the Penguins were to move Rakell there are Sillinger and Mateychuk. I have a feeling neither would be achievable, because both are playing significant roles on Columbus right now, but Sillinger especially would fill a huge organizational need in the long run.
Only 21 years old, 29 points in 54 games with no PP production looks really solid. With Monahan and Fantilli down the middle, I feel like Columbus could survive moving Sillinger if they wanted to. I'm just super doubful they would move him, at least for Rakell, and Mateychuk feels even less likely.