I've heard that center is a very difficult position for a rookie to take over. Wood seems like he might be able to do it though. Why you'd put Hangartner on the bench is mystifying. I'd go for (Bell, Hangartner, Wood, Butler, Walker)
What worries me is that back problems can become chronic for a player and here's knocking on wood it doesn't continue. (No obvious knocking wood jokes. )
So you've never seen depth changes on any other teams? That's what camp is for. Guys the coaches may not think are ready will come along much faster than expected. The Bills are not the only team to change their depth chart after camp and those other teams don't have bad "roster watchers"