Moving a LB to play DE is not unusual. It it pretty common to take a high school corner and make him a safety, a high school safety and make him a LB, a high school LB and move him to DE, and a high school DE to DT. For example Huynh was a DE. The same thing happens on offense, with TE's becoming OT's at the college level (thing Chris Rogers, a couple years ago). It doesn't always work, but when it does, it often works really well because as they add size, they keep quickness.
L.C. I have seen some QBs convert to safety very successfully.