If the Rams wind up with someone that is unknown, or has been portrayed as on the "C" list, it is not going to go down well. Fair or not. There will be no patience in LA fandom for an obscure HC to prove himself. For one reason, it'll appear that he's the best they could entice to come to the Rams, or that the FO continues to have no idea what they're doing. This hire had better bring some credibility and reason for hope, or there are going to be a ton of empty seats.
Perception is going to matter greatly to fans and to the media who greatly influences fan attitudes. And likely to the players as well. They can say all the right things in public; but the reality is that if they don't have a sense that a particular hire is going to be a real asset, he's going to be a real tough sell.
This is why if an OC/DC is the pick, a name like Shanahan (with some real credentials at least so far as offense is concerned) ought to be #1. It is one thing for the Steelers to hire an obscure young LB coach and make him the HC; that is a successful football organization with a long history of winning and stability. But that won't work for the lowly Rams who have made losing into an art form.