You're overthinking this. In the end what you're proposing could happen I guess but by no means is this a real option to debate right now.Maybe because the plan could be to target safeties and turn them into LBs? Speed kills.
Question is: would you rather have a slowish 4-star LB or a fast 3 star safety? LB is probably stronger and more ready to contribute immediately (maybe gets reps as 3rd teamer), while the safety needs a year or 2 in the weight room, but when he's ready his RS Sophomore year, he can run and hit like a truck. Really not a right or wrong answer, just depends what kind of defense you plan on running.