Trading down works when it's later picks. There's a more varied opinion on who BPA is, and teams are more willing to pick by need than BPA. That's why Mantha/Bertuzzi for Mirco Mueller and Cholowski/Hronek for Chychrun worked.
Dropping 4-5 spots from #6 is a whole different ball game. Hughes and Kakko are gone. If I had to guess, Turcotte, Byram, and Dach will be gone. That leaves us Zegras or Cozens to pick at 6. Guarantee both will be gone by #10, and I'd bet Boldy is gone too. So that pretty much leaves you Podkolzin, Caufield, Broberg, and Krebs, all of whom have question marks hanging over them.
Not worth it. We already have three 2nd round picks.