I doubt anyone knows anything about deeper mechanics, right now (aside from the devs of course, but they won't tell)
But slowly uncovering all these bits of info in upcoming months is what I'm really looking forward to.
Though small part of me is screaming "Don't watch the streams and previews! Go blind into it! You will enjoy discovering everything for yourself."
From what I have heard we will be able to change a few things with the Dinosaurs like color and maybe some other small physical things like the Deinonychus that had that crest on it's head.
No we won't be able to make a T-Rex with Triceratops horns and a Stegosaur with a Raptors head.