I think that would be the perfect spot to pick him up. Then you take either OL or QB with pick 40. Just don't think DGB will be around much longer and he has as much potential as Cooper and White. With our playaction he would be deadly.
I had DGB going to the Rams in my last mock draft, but the only thing that gives me pause about it is Sneads comments when they drafted Jenkins. He mentioned that having the extra picks in the round that year made it much easier to take the risk on a player with such issues.
While you can't doubt the talent I worry that the proximity of Springfield and Columbia to STL may make it to easy for the undesirables to make their way to STL.