Your argument is basically saying that a first draft of something is more canon than the final version. That is a ridiculous proposition. Yes, it would be interesting to see how the game evolved during development, but the final product is the canon version.

This doesn't mean that they did change anything. It's probably most likely that they had finished all of the development of the Rinoa model, but not for Selphie. Therefore it was easier for them to chuck Rinoa for the earlier demos, and replace her with Selphie when they had developed her model.

But even if the developers did change their mind about Rinoa's character, that is their rght. It is the final product which matters, not what they did beforehand. I am not going to believe that the storyline of a first draft of a novel is more correct than the final, published draft.

It would be interesting to see how they developed the story in Final Fantasy, but the developers chose to have a certain story when they released it. Any storyline which was scrapped during development is exactly that - a scrapped storyline.

Basically, it would be interesting to see the development of the story in VIII. However, nothing in the initial storylines has any impact on the final storyline, and is therefore non-canon.