Sure, they should try to trade down, I agree, good luck to them in doing that, but will it actually happen? In that article they talk about it being a very deep draft class, which is why the Lions should move down (along with saving a bunch of $ they'd have to pay the #2 pick), but precisely because it's such a deep class with no standout #1 franchise QB and all the salary arguments he makes, is the EXACT reason it will be difficult to trade down, unless they basically give the #2 away to avoid the money hit.
So, if they can't trade down to get more picks to shore up all the gaps they have, they need to find a way to get high quality players outside of the draft, so either free agency or trade away a player other teams would pay a lot for. Who do the Lions have that other teams would actually want? Calvin Johnson. Outside of him is there anybody?