I get what you're saying. Maybe it's just me. I think I worry too much
I completely understand your concern, but I will point out, in addition to the points made by other posters, that....
If Luck had to play his first 2 seasons under two different coordinators, I think B.A. being the first of the two works out pretty well. B.A. basically threw Andrew to the lions this season, which has prepared him to do things in the offense that rookies are not normally asked to do. Hopefully the added responsibility of having to throw down-field with defenders hanging from you will make anything he has to learn in a new scheme easier to pull off for him ... There hasn't been great chemistry or timing between Luck and any of the receivers this year except for Reggie and maybe Allen... Hilton and Avery get open running go routes... I guess I'd have to know who was replacing B.A. to really delve into my feelings about it... I'm not crazy about unknowns...
A couple concerns about having a new O.C. that have popped up in my head while writing this post:
1. personnel- I don't know if any coordinator other than B.A. would prefer the small speedy guys that we have over tall, physical guys... T.Y. has a chance to be an outside guy under Arians, but will probably be permanantly relegated to the slot under anyone else... dunno if that is good or bad... believe it or not, we do actually have some tall and/or physical players to catch endzone passes and block as it is [(Fleener/Allen/Reggie) Reggie is a vastly underrated blocker, and a sneakily physical receiver, but not a great jumper]
2. control- Arians had a reputation when he came here as a guy with a system who was going to run that system regardless of personnel... I think we have seen however (more at the end of the reg. season), that he is willing to alter the system to fit the strengths of the team... if we bring another guy in here, will he come with a system and will he want to find his own player-types to run it?
B.A.'s personality seems to fit this team and we are winning as a result of the cohesion and chemistry that we have between the players and the staff... I know that Chuck sets the tone, but we can't have dissonance in the locker room with such a young team.
If we do end up with someone else, we need a full off-season and preseason to get the playbook down and develop timing. Don't forget that we will have some new faces and some players returning from injury that will be starting basically from scratch anyway... so... I don't think that the sky is falling, but I have been so pleasantly surprised with Arians this year that I do hope he comes back to nourish what he has helped build... Who knows, maybe Ken Whisenhunt is Andrew's offensive soul mate. I guess it is too early to know anything atm.