Eto's kakuja probably looks different because it evolved over time through continuous cannibalism.
Maybe I'm over thinking this thing, but trying to understand the Mangaka's train of thought is nearly impossible so I'll try to use this page from chapter 34 to see if it holds its own.
http://vatoto.com/read/_/220264/tokyo-ghoul_v4_ch34_by_twisted-hel-scans/13
Now in that page Itori, and Uta bring up a few things that are interesting to say the least:
Itori: Back in those days the eye witness reports were preposterous. It's not even certain whether it male or female. There was even a report that it was an old man wasn't there?
Uta: I heard that it was a small child. A child in my ward claimed to have seen it.
The old man that Itori heard about was Kuzan
The small child (at that time) was most likely Eto
The male one eyed Ghoul was Kuzan's kid 'real One Eyed Owl'
If two out of the three hints in that page were true, then couldn't the third?
Also if you look at Eto's hair, it doesn't resemble either Ukino, or Kuzan in the least.
Let's assume that Kuzan is her father, then who is her mother? Eto's hair is not only a different color, but a different 'kind of hair' (not curly, or straight (like Ukino and Kuzan but something different, I can't find the name for that specific kind of hair)
Now the interesting part, Kuzan can mimic the One Eyed Owl's exterior looks, and his (supposed) fighting style right?
So why do they look so different, they're supposed to look very similar to each other in their Kakuja form, but Eto looks nothing like Kuzan's Kakuja form.
In the previous page to of the linked chapter Itori says that the one Eyed ghoul she had heard about (Eto) had/has an enormous appetite which as you said could explain her radically different exterior to Kuzan, and you're right about that.
But ask yourself this, in chapter 34 three One Eyed ghouls are hinted at, two of them are confirmed later on (one of them being Kuzan in disguise) then would it really be that far fetched that the third one existed as well?
In Itori's conversation with Kaneki she refers to the one Eyed ghoul as 'him', Uta brings up a small child, Itori brings up an old man, so wouldn't the third be an adult in his mid 20's or early 30's because she doesn't feel the need to specify his age.
TL;DR I personally believe that the 'real One Eyed owl' is both Eto's father, and the One Eyed King.
I may be way off base here, but I was able to predict that Kuzan wouldn't die in his encounter with the CCG, and that he was going to be used to create more artificial ghouls, so I do have a good deal of confidence in this one.
Also while I'm at it, who here thinks that a Manga like TG would be easy to predict?
Certainly not me, Eto's father not being Kuzan would be more of a surprise shock for the readers then her being his doughter even though she is supposed to have white semi curly hair (I think)
Regards
Dibbs
Edited by Dibbs, 16 September 2014 - 12:28 AM.