FWIW, my impression of the message of multi-limbs on Blue's creatures is the opposite
that some others get. Having four limbs is not a universal ideal or baseline (as our arthropod cousins show); it is just an evolutionary by-product of the basic earth vertebrate pattern.
So rather than seeing multi-limbs as an alteration, I see them as a way that Wolfe marks certain creatures on Blue as natives; others are are alien invaders. This could be a clear message that Blue is not Earth or Urth or Ushas.
Also, I suppose it has been mentioned before but I just re-noticed Wolfe's description of Inhumi as not being good with tools. Add this to their parasitic and mimicking nature and I think the connection to Shadow Children becomes quite powerful. This might make Fifth Head of Cerberus a very fruitful place for understanding Inhumi origins and how they think and feel as they assume a new identity.
-bsharp