Sadly there won't be any Plague Marines at launch, but hey whatever works for you man! They're very likely-almost confirmed to be coming out post-launch though, so there's that.
They are confirmed, read the post i linked on page 23. David also mentioned in our little back and forth that even if god dedication will be worked on further after launch that they will still make the Marks of Chaos (for each respective god) available on launch. It is said also that you will have to earn them. Add to that the post by Brent quite some time ago that said that accessories will make you technically able to roll a "Nurgle build": "==Chaos Gods== At launch, the Chaos Gods will be present, but not out in full force. That's going to be coming with time. Instead, expect to see the Chaos Gods flavour your builds with accessories. These should be major accessories though, so we fully expect you to be able to call this a "Nurgle" build, or a "Khorne" build, etc. You're just not devoting yourself yet, so you can switch it out at will. Psychic powers are generally pretty tied to specific gods, of course. This lets us give them more flavour, but is also handy for balancing purposes." http://forum.eternalcrusade.com/thr...ke-in-eternal-crusade.802/page-90#post-187201 So pseudo Plague Marine will probably be there, along with Black Legion being one of the starting legions people can easily replicate the Bringers of Decay warband.
I could be persuaded to just go Raptor, on the basis that a Man-Reaper + Jetpack combo would be pretty devastating.
