The Canucks need a 1D to pass to the top 6 you want, so that top 6 can score...
If you mean replacing those players with 1st rounders, then you'll have 30 goals collectively for the year.
The Canucks have the prospects in place already; Shinkaruk, Horvat, Jensen, Lain, Archibald, Corrado, and that does not include Tanev, Kassian and Stanton.
At this point, building around the Sedins has been done an the Canucks went to a game 7 Stanley Cup final.
Now it is time to build a new core withing the next four years for a smooth transition. No need to blow it up and wait for ten years.