I know that this is a long time coming, and I don't know if someone else is working on this, but...
Zurvan, the Ancient One.
As a fully-modeled, fully-animated, fully-programmed, usable hero unit.
Scaled down in size, of course, to somewhat the size of an Omegalisk, so he can join the ranks of other (Primal) Zerg forces.
Lore-wise, it would probably be best to refer to the unit as Zurvan Spawn, but I still think it would be a great asset (pun not intended) to repertoire of heroes and potentially frontline soldiers. His love for Quillgor meat would suggest a biting-type attack for melee/anti-structure, plus an anti-air swipe of his claws (BTW, we don't see too much anti-air melee, do we?).