Bostic is far and away the best option in the middle at this point. I think he may yet turn into a pretty good player. Has to be healthy though. You don't see many crucial defensive players with constant injury concerns like you do with skill guys on offense, so he needs to get on the field and put this behind him.
As for scheme, when you have every Tom, Dick, and Harry you've ever scouted out on the field, you just can't do much. Half the snaps, we don't even have the play caller on the field. Getting Briggs back will be helpful in that regard, but you still have guys that are just jumping into our system.
One thing that it will be interesting to see play out is what the FO thinks of everyone irrespective of performance. If the feeling is that Trestman has a special mind for offense/football, they'll be willing to see more s*** go downhill and place blame elsewhere than if they've been uncertain from the get-go. Same for anyone else involved, of course. Just like why we've dealt with so much Jay Cutler BS. We could all see a special QB in there somewhere, so sometimes we chose to disregard current performance in hopes of seeing that good guy come out.