On Giger's 3 design - Stuff like the dome frilling open is a bit much but other new details like the lips, tongue and claws I'm fine with. I see it as no different than the exposed ridges and arm blades on the Winston warriors, just variants the species can take on, especially if it's a quadruped.
The tail does look a bit off but if I'm honest the big meat cleaver at the end of the ADI design has never done it for me either. But overall I really dig the unused design, it's just so sleek and sexy. I would be tempted if NECA ever got to it.