The best option may be trading a 3rd rounder for Darnold if the Jets get the no1 pick, and having him compete with Eason next year for the starting job. I also wouldn't mind signing Kelly back since he knows the playbook and has potential still. A competition with those three wouldn't hurt us much in the way of draft compensation, we can figure out if we have our franchise QB within the three, and still have a solid draft class.
Heck, in this scenario, Ballard could trade down in the 1st to acquire the 3rd round pick back he traded for Darnold. I trust his drafting skills enough that I believe he can hit on a late 1st round pick.