The aliens take on the body shape of whatever they incubate inside. That's why most of the aliens you see are humanoid.
Of course, but that's part of the Alien mythos already, so I don't think having an alien that took the characteristics of another creature than a human counts as a radical redesign.
Also, they're not going to not have a human chestbursting scene. We haven't had a decent Alien film for years and that's going to be something that Scott will want to do right.