Look, with Batum's cap hold, the draft pick holds and the players on the roster, we have 41.3M spoken for (actually, including the minimum roster spot hold it's 41.8M, but once we sign someone it won't matter so I'll ignore it for now).  Guesses from guys like Hollinger say it's going to be around 61.5M cap this year.  That leaves us 20.2M under the cap, since Hickson's been renounced.
**All assuming IND doesn't match.  If they do, it's all moot anyway**
Hibbert's "max" deal will start at 13.7M, based on the cap guess above.  That gives us 6.5M to get other free agents, and then to match Nic's offer, if we choose.  Freeland's being assumed to come over for around 3-4M (and we have to use cap space for him), leaving us around 2-3M for a backup PG.  
Now, if we S&T Nic for just Williams, Williams' salary of 4,809,840 would basically replace Nic's 5.4M cap hold, so we'd have 7.1M to spend on FA's after maxing Hibbert.  If we do Williams and Webster (and cut Webster), Webster's cap hit after being waived would be 600k, which basically makes it a salary cap wash.  We'd still have the same 6.5M to spend that we would've after Hibbert, but we have Williams instead of Batum.
Where it gets tricky is if we take back Ridnour or Wes Johnson with Williams.  WJ's 4,285,560 (or Luke's 4M even) would cut into that 7.1M space.  So instead of Hibbert, DW, Freeland and maybe a backup PG...we would have Hibbert, DW, Ridnour or Johnson and less than 3M to fill the roster before we use the Room Exception.
It wouldn't crush us as long as it's ONE of Ridnour or Johnson coming back with Williams...as long as the cap guess is right.  If it's only 60M, it's even more vital to not take the second contract back from MIN.