Center is probably the best position for him because he's the most protected there from his lack of great strength. He plays with good technique and he has good movement skills for pulling, etc. His one issue is power and center takes the least amount of power.
Frankly, the reason I wanted to give him a shot at the backup LT job was similar to that. Sure, there are some power right ends, but most of those guys are built for speed. Williams was never built for taking on 300-plus-pound defensive tackles, at least not by himself. At center, teams will be able to isolate him at times, but most of the time he's going to have a little help.