Those are easily correctable learning experiences. Weist is a gem of a coach, he's managed to get the offense going which, given a relative lack of playmakers (saving Geremy Davis), is quite an accomplishment, and clearly the players respond to him. Anything related to offense, I have confidence he can manage and learn from his mistakes.
But it's still a big step up to manage a whole coaching staff and team, oversee recruiting, and so forth. I personally would like to see something like Narduzzi as head coach and Weist as OC, but give him a big raise. Let him get some experience as a coordinator and maybe give him some extra responsibilities to prepare him to be a head coach. Then if Narduzzi moves on, Weist will be ready.
But I would not mind if Weist ends up being the hire. I have confidence in him. I just think he might need some time to establish himself in recruits' minds - it could take years to prove he can get guys to the NFL, to build up recruiting connections, and to get a staff solidified, since he's never worked on defense or had to hire defensive guys. If we had a guy like Narduzzi and retained Weist, we'd have defense and offense covered, plus visibility with recruits. Weist would be a solid low-budget alternative in my mind.