Eric Bieniemy would have made a ton of sense as the Steelers offensive coordinator
An obvious option that might have been a better option over Arthur Smith was Eric Bieniemy. He left the Chiefs recently to try and prove that all of his success wasn't solely from Patrick Mahomes. He went to Washington and was able to make a competent enough offense out of a messy roster. Bieniemy is someone who probably deserves a top job in the NFL but has not been able to find one since his rise in the coaching ranks.
Most of the reasons behind him not getting interviews right now is the stalemate that his current organization is in. They are currently without a Head Coach and Bieniemy is up for consideration. It sounds like they might go in another direction rather than hiring their current offensive coordinator. It sounds like Washington wants to go with a younger individual or someone with prior Head coaching experience like Dan Quinn.
If that becomes reality, it seems like Bieniemy will be looking for a new gig elsewhere as an offensive coordinator. Tomlin should be calling him on the regular to try and convince him to take over an opening on the Steelers staff. We know that he is not afraid to reach out to coaches that he respects to try and convince him to join the team. Pittsburgh could try and get Bieniemy in a quarterbacks coach and passing game specialist role.
If he can fix the putrid Steelers passing attack, then it seems like a Head coaching job would be a sure-fire bet for Bieniemy. It might take some convincing, and many other teams will want to try and bring him in as their next playcaller. It would be a huge swing for Tomlin and perhaps the ideal scenario for the black and gold to finally fix their offense right away.