I disagree with the point about WRs in the 1st round. I'd be shocked if Chase, Smith and Waddle weren't at the very least good NFL WRs. Chase and Smith will be gone by 13 and Waddle would be a 4th in preference behind the 3 positions you mentioned initially but I'd be happy he he was the pick. O line is the obvious pick by far though. Probably should be taking 2 O Line guys in the first 3 rounds.
The defensive system will probably depend on who comes in as DC I'd imagine. I know the Rams ran a 3-4 but I don't know if that is Staleys preference or if they kept it from Phillips. Nwosu played OLB in college I'm sure, so he could move there comfortably I imagine. Murray played better towards the end of the season, he will be fine I think. Perryman should be re-signed, on a cheap deal though given he gets injured all the time. If they stay as a 4-3 I could see Tillery moving to the edge he played there a bit when Bosa and Ingram were out and actually got a bit of pressure on the QB, something he never done when he was playing inside