I wouldn't do this.
At this point, I'd rather have T-Rich over CJ. Couple of issues: 1) Appears CJ may have been a tad overvalued on draft day. He wasn't bad at all this season but the gap between him and other elite WR #1's seems to do more with consistency. It was nice to see CJ get TD's this year to along with his monster yardage.
But this is the year of the lack of elite RB's. You can look at it like, well, that means I'll be similar to other teams with bust RB's. Or, you can have a clear-cut advantage with an elite RB. If not AP, McCoy or Charles, luck out with Bush, FJax, etc. In the case of T-Rich, signs point up compared to his value a couple of weeks ago..and he may end up as a late-end RB #1 which is where he was drafted.
Let me get this straight. He currently rosters 4 QB's?! He's trading away CJ and he only has 2 RB's?
You hold the leverage. He really needs RB help. T-Rich's value should increase. I think you'd either bench Rivers most weeks, in which case this deal is pointless, or, you'd be iffy about playing matchups between him and Ryan.