Yeah I am aware of all that. This trade scenario has been discussed, a lot, on the main draft, trade and free agency board. And in this thread and/or the draft thread at least twice before.
Personally I don't believe Ballenden will be bid on before pick 18. And if he is, I'd be seriously tempted to not match the bid.
Lions should trade 18 to GWS for 23 &25, use 23 for Cameron and leave 25 for Ballendon. Therefore, get both for 18.