I look at our best 23 from last year and we have essentially lost ANB and gained Langford (and maybe Lindsay) into the side. With ANB gone, we lost a lot of transition running and pressure acts, but with Langford arriving we potentially added a better kick and better mark in the forward line. So the ANB replacement will be Langford.
I don't see Rivers holding a full time spot in the midfield if Petracca, Oliver and Viney are all playing (and I prefer Rivers at half back anyway). Pickett needs to have minutes in the middle as well because he is elite in centre clearance. So I am not sure Langford will get that much time playing as an inside mid.
That all said, we need to find a way to replace ANB's transition running and pressure acts. While Langford should be good in these areas of the game, ANB was one of the best in the AFL and had completed 10 AFL preseasons. I think the best solution is to play one less forward target (Fritsch and only two of Petty, Turner and JVR). Petracca and Langford (and maybe Melksham) can play minutes as another hybrid tall target/small.