The only position or role that we do not have sufficient depth at is PF. We don't have a starting quality PF and we don't have any real depth either. At every other position, I feel we have plenty of depth:
PG: Kemba, Smart, Pritchard
SG: Brown, Fournier, Langford
SF: Tatum, (Fournier), Nesmith
PF: GWill, Ojeleye, Parker
C: RWill, Thompson, Kornet
To me, the PF position clearly stands out. The C position is a touch light but it would be fine if we had a decent PF to play. You can get by with limited centers if you have a good PF but it becomes a glaring weakness overall in our case. We don't have even 1 true starting level big on our team. Not 1. Unless you are the Nets, that is not going to cut it.
There are some PFs/Bigs that I would go as far as trading Brown to get but not too many. And I would not trade Brown for any guard/wing depth players. Never.
For example, Brown for Towns. Trading star for star but balancing out our roster. I would trade Kemba for depth but only if it included some big depth (understandably that is not going to be a star).
Now if we don't sign Fournier, then that does create a depth issue at wing. I am not sure we can count on Nesmith and Langford to cover that but they might. Obviously, we are better served with Fournier if we can afford him.