Losing BOB could fall into the "be careful what you wish for" category. I think O'Brien's move back to the NFL is what he's been planning since he got fired by the Texans. He was a good coach, but a horrible GM, and has always been an NFL guy except for his early years and the post-Sandusky/Paterno "savior" role. I personally think the issue for Alabama on offense the last two seasons has been the lack of development of the WR room and the mind boggling issues with the 5 stars on the O line.
I expect Saban to go the NFL route for both his new coordinators. There's been a cycle between NFL and college offenses and defenses and that cycle is now NFL influencing the college game whereas 5+ years ago it was the opposite. I think Saban sees how Kirby Smart hiring Todd Monken is what put Georgia over the top. IMO Saban saw that in O'Brien, which boggles my mind as to why he isn't addressing the WR and OL coaching. And NFL defenses, namely Bengals and Ravens, are showing how to control the dynamic downfield, spread, and RPO-based college offenses that have become the norm in the NFL starting with the 2017 draft. Who knows. We'll see. Saban doesn't strike me as a fun guy to work for and he's not getting any younger which makes hiring the right guys more difficult, but all of the success and that roster certainly is a strong counter-balance.
I was hoping Ryan Day would look to the Kyle Shanahan or Sean McVay tree for his new OC, especially given that Zach Taylor's staff is just an hour and half down I-71 from Columbus (and Taylor seems to have figured out the new NFL defensive schemes). But, he promoted internally. The best WR coach in college won't necessarily be the best OC and if it's another Peter Principle hire by Day, he'll be gone.