I like Simmons a lot, just not a fan of waiting a year. His off the field issue bothers me, but not enough to keep me from picking him (assuming his interview covered it well). While the injury itself is not a show stopper, it's much harder rehabbing a 300ish lb guy as opposed to someone leaner. And getting back in game shape takes longer.
As for him at NG/DT, he officially played NG at MSU. He was moved around a lot though. Most project him to DT. He like Tillery can both be moved around the interior.
Another thing that concerns me a bit, is how much of his success was because teams were focusing on Sweat. Whenever you have multiple high achieving guys in any unit, their play is raised because of others.