It's positionless basketball. Simmons and RoCo are forwards. RoCo's really a stretch 4 ... I don't want him guarding good offensive 3s because his lateral movement probably is the worst thing about him on defense, but he can body with a lot of 4s these days. And Simmons would be handling the ball a lot.
I'm still not sure if Simmons works with the Blazers. I know everyone wants to be rid of CJ and is clamoring to get better on defense. Simmons would take care of the first and seems likely to help with the second. I think the Blazers offense would take such a massive hit, though, that it might not be worth it. You have no real No. 2 option. Powell's a great No. 3 option, but he's not creating a ton of offense all on his own. RoCo? He's a streaky set shooter. Nurk lives on the pick-and-roll.
If you can trade CJ for Simmons and Nurk for KAT, now you have something interesting.