Good post. My feeling about this is that both moves can be made.
Can a guy like Bieber be traded for someone like Santander? Would Elias do that? Would Cleveland? If not, would there be some other combination of player(s) on the 40-man roster to acquire Bieber? If you do that, you can still use some of your young depth to acquire one of the Marlins/Mariners young guys.
I am not sold on Cease as "the guy" to put them over the top. If Elias feels he is "the guy", then I feel a little better about acquiring him. For me, I think Bieber is a more realistic, albeit possibly a less effective, alternative. But, if acquiring him allows them to acquire another young arm to put into the rotation, that combination could be worth more than a Cease acquisition alone.