Mundy deserves another year. It's worth taking the punt on Bennell for another year with very little downside.
Ballas might have been a bit lucky, but by all reports he's one of the best trainers at the club, and has taken a few young guys under his wing. We're losing Johnno, Spurr and D Pearce this offseason, which is a lot of leadership, so as long as Ballas is comfortable sliding into a mentoring role - and can accept some spells at Peel - I can't see why you wouldn't get him to go around for another year.
I'm not sure how many slots we need to open for drafts/trades, but with three guaranteed open slots we'd probably only need to find a few more. Most on here would pack Sheridan and Sutcliffe's bags for them, for example, so I don't think finding people to cut will be too difficult.