I'm not really fussed about Mavs, tbh - he's a loose end, and the designer in me likes thinks to be neat and orderly, but he's also relatively inexpensive, and he probably won't bring in much money, so I guess we can afford to wait and see if Germany can turn him into a serious player for us.
The one thing that's making me think that we should maybe keep one of those CBs is Luiz: he's only on a one year extension, and he's also only really useful in a back 3. And if we're still going to be playing a back 3 every now and then, then we might night need more than 4 CBs across the season?
Careful what you wish for though, because we might not end up with the option that you want! If I were Holding or Chambers, I'd be looking at the players coming in and thinking that I'm basically going to be fighting to be 4th or 5th choice at Arsenal? If they were on £100k/wk+ contracts then they might be happy with that (in which case you wouldn't really want them anyway), but I think the two of them are actually on relatively low contracts, so I wouldn't be at all surprised if they both requested moves? If any one of them ended up staying, there's a fair chance it could end up being Mustafi!