I think you're looking at this the wrong way. You said that people with the same soul/heart can exsist in many different worlds. Using Sakura as an example to justify that, both from TC and CCS are kind, innocent, altruistic and true to their emotions. However, they are still two different people raised two different ways. One is a school-girl who's active, energetic, and speaks her mind. The other is a princess who is quiet, withheld, yet eternally trusting. So, although they are different people, you can see how one, raised in the other's world, would turn out the same as the other. right?
Ok, I ran in circles there, but just keep that in mind. If a person turns out to be a certain kind of person regardeless of upbringing and enviroment, it's logical to assume that they share the same heart/soul, or that the soul is a direct and major influence on the evolution of a person. As such, that person, in two completely different worlds, would be able to think and act the same way. If they think and act the same way, their imaginations would be the same, if not closely simmilar than. right?
Ok, my point is coming out. You said that Fye was implied as the creator of Chii. If so, than is it not understandable that two different fye's from two different woulds could have simply created Chii the same because that's how his mind/imagination works? I wouldn't call that balance, I'd call that inevidability.
The same holds true for Tsumomo and Kotoko. They were characters in a game, so their creator simpl used their models as it came to his/her mind, the same way the Laptop persocoms were created in Chobits. Now I have nothign against Chii or her having a soul, but this should proove that she doesn't need one to appear in multiple worlds.
This brings up another issue though, following my trail of thought obviously. Chii in Chobits really did have a soul, I believe. However, since she was a creation, than her soul was created as well. Now, if Fye from TC created a Chii with a soul as well, than that Chii would closely resemble the Original Chii, as much so as a person with his counterpart. However, since their souls were created indevidually within their own specific universe, would they still share the soul?
Somehow this brings me to another trail of thoughts. If the same person from different worlds really does share a soul, what happens if they meet? What would happen if Fye or Kurogane or Syaoran appeared in a world that they existed in allready? Einstein said that a person cannot be in two different places at the same time. Now this applied to time travel, yes, but with a sharing of the soul, wouldn't it work the same in dimentional travel? If Sakura came to the CCS world, and met the CCS Sakura (assuming that they are the same person in different worlds) Would one of them dissapear? Would the universe end in a paradox? Would the CCS Sakura absorb the TC Sakuyra's feather instead, thus preventing the ultimate completion of their multi-dimentional quest to begin with? My head is spinning with possibilities. and I can't apply any of my time-travel theorums to understand it, because the multidimentional axis is completely perpendicular to the temporal one. Kuso!!! Not I've got to read through "The Number of the Beast" again. DAMN YOU ROBERT HEINLEIN!!!! THAT WAS ONE OF THE MOST BOORING BOOKS I'VE EVER READ!!!!
....um.. what was I talking about again?