WS once confessed to me that he taught Dalli how to build theories. Knowing this, I would prefer to keep the Dalli side of life within limits
I mostly agree with you, bro, but what else can you do while waiting for the next update instead of coming up with theories?
Although the visual similarity between the characters is a very weak basis for concluding that they are related. Many 3D assets are reused by the same developer, and this is a common practice. On the other hand, this gives the author room for maneuver; Behind the scene, he can change the relationships between the characters (until they are established in the released chapters), make them relatives or vice versa, and we will not even know about it.
To me, the most plausible argument that Nika is the offspring of W.Z (or one of the Zanes) is the fact that Ayua is Zane, and she's not a LI. Knowing that the canon version of the game does not feature incest, it makes sense if Nika and Ayua are related. But, if I remember it correctly, Ocean said that he would no longer disclose information about new LIs, so who knows, perhaps Ayua’s role has already changed.
So Nika, being Zane, becomes quite limited in his choice of LI, since he cannot mate a Zane offspring. And everyone who is a product of the loins of the W.Z will become unavailable to him due to possible incest. Although of course, in the canonical version of WiAB Leia and Katie are just an old friends...