>>9900789Apparently Xi is mainly about enhanced atmospheric flight capability. Since Byarlant and Zeta were both made with advancing that in mind, I see it as a fusion of the two in a sense. Right down to the less orthodox head and big triangular shapes.
But the designer and/or author not going the route of making it so advanced that it's just as, if not more sleek (but no need to transform). It's that idea of a bulky/big prototype/non-final tech, which they'll eventually try to downsize.
