You can never have enough A-graders in a side. Besides, even if Viney, Toumpas, Trengove and Watts miraculously turned out ok, Melbourne would still be around a 6-8th ranked side. Think Carlton: Murphy, Gibbs, Simpson, Judd, Scotland, Carazzo. If Hogan turns out ok, then the comparison is St Kilda: Riewoldt, Hayes, Dal Santo, Goddard, Montagna (and Ball) - still didn't have enough of a cutting edge to win a premiership even with those players.
If we can't get an instant A-grader via trade, then Melbourne ought to draft someone with A-grade potential and bloody well develop them properly, for once. If this Roos is as good as he is getting paid, he should be able to pick the right rookie and develop them properly.