It seems to me that if the Blazers resign Mo Williams to the contract he will seek and deserve the team will be committing to him as the third guard in the rotation. If Williams is running the back up point and playing in the back court with Damian Lillard sliding to the off guard for a few minutes per game that doesn't leave much time for your fourth guard.
To me it doesn't make sense to use a lottery pick on a player that you plan playing spot minutes as the fourth guard or as a player you groom just in case a front line player gets hurt. There are cheaper options for that type of role player.
I think the Blazers need to make a choice now, commit to CJ as the third guard in the rotation or trade him while he still has some value. Trading CJ for a young back up center or forward would make more sense if you're going to move forward with Mo Williams.
I understand the desire of going with a vet back up, based on how the Blazers play last season, however I think going with CJ and maybe a cheaper vet that could be the fourth guard and mentor would be the better move. I actually believe that a CJ and Will Barton bench back court could be effective for two or three minutes per quarter, the only problem there is I'm not sure either would be ready to step up and start if something happened to Lillard or Wes Matthews.