I'm not that high on Simmons as a whole, but as a Draymond replacement he'd be an upgrade. He could play anything from the 3 to the small ball 5, great D (pause), better scorer, can run offense through him like Draymond (Simmons is a better decision maker with the ball), etc.

If you have him and Dray on the same team though, he loses a lot of his value, as you now have another non-shooter clogging up the offense and not doing much off the ball.