I really don't care about who is NHL ready. This team's fortunes for next season do not hinge on whether 18 year old Sam Reinhart, Bennett, etc, crack the lineup. Even if it means having to roll with Gagner for another year, I don't care. I want the best player, not the most NHL ready player.
Yeah, NHL readiness should be WAAAAY down the priority list when deciding on a prospect. Whoever the Oilers draft isn't going to change their fortunes one way or the other for at least a couple of years so they need to take who they think will be the best player long term and who will be the best fit.
I'm fine with any of the top 4, they all fill needs and in different ways. It's pretty unique to see 4 players at the top of the draft all with completely different skillsets with Ekblad - Seabrook, Weber or Reinhart - Bergeron, Toews or Bennett - Richards, Kesler or Draisaitl - Kopitar, Thornton.
The Oilers have so many needs that any of those players would suffice.