I would take...
RB Robert Quinn (safest pick and elite player) -unfortunately HB careers tend to be shorter than most positions
RDE Eric Williams (fairly safe though he could decline some) - DEs tend to player 12-15 seasons so they have some of the longer careers
MLB Terry Born (fairly safe and the most ready to play right away) - LBer impact in this sim can be iffy, but Born could easily be played at DE and be an elite pass rusher or be used as a blitzer from the LBer position.
QB Calvin Valves (he's a safe pick in that he won't decline much, he's a statue in the pocket. He will most likely take a ton of sacks in this sim. With his speed I wouldn't take him anywhere in the first 3 rounds.) - QB play often feels random, I couldn't justify a high first on one that can't run.