I don't have feelings either way but if I were to choose make them eligible for the minor league draft (too late for the major league draft and does not make sense for waivers unless they are not picked in the minor league draft)
I realize the age makes in not appropriate for the minor league draft but the other options (waivers and next year's draft) seems unreasonable. Since he has never played in the MLB, the minor league draft makes the most sense.