That's fine and its something I'm still thinking about for a fic so its not set in stone.
In my thoughts, Ansem doesn't see replicas and nobodies as the same thing but isn't willing to acknowledge Xion or Riku Replica as a fully fledged person. Remember replicas are basically robots and as a scientist Ansem wouldn't be against creating autonomous drones. However he would be against artificial intelligence and warn against giving them the ability to think for itself.
Namine and Mickey disagree and later Riku will.
Nobodies to Ansem are unnatural because of how they are formed. He sees them as more akin to ghosts or demons.
A replica is just a more elaborate tool to Ansem.
Xion and Data sora were created by nomura to talk about 'what is the measure of human being?" and I reinterpreted it to be "what defines a life?" as KH makes no distinction between Mickey and Riku as sentient beings.
I wanted to keep that theme but play with it more thoroughly than the game does. Or atleast in a way that develops established characters as well.
It seems to me or replica are more like homunculus rather than robots?
The same Xion was equated to nobody, however unlike them it was grown artificially.
Riku-Replica had emotions and nobody denied it, on the contrary they still (Organization 13) and manipulated it.
If you take all of the above, then their creation becomes even more monstrous.
In fact, they created almost full-fledged people and eventually tried to make them puppets / robots.
As for your story, I still do not understand the point of DIZ to create a copy of this scenario.
Riku is not skilled enough to fight Roxas?
Yes, and this narrative can greatly affect the plot of KH2 and RAX trio in general. For it would be necessary to further develop them as a trio (For perhaps the story is the same as you said, they would probably also later in the future, after KH3 would become a trio) preventing further development of other equally interesting connections in the series. (For example Lea and Kairi)
However, as a fanfic of AU, I really like it. I love fanfics with an alternative fork of an event like "What if?" so I'll be happy to wait for your letter. ))
I apologize if so hard I try to prove to you my point of view.