What is the "official" version?Yeah, I see what you mean - at the same time I must say I love Seven so I don't mind her being involved in so many episodes so intensively.
Also, I guess by now everyone knows the "official' version why poor Kes got the axe. However, I sometimes wonder whether part of the reason might have been that producers already knew how everyone else would be pushed into the background due to the introduction of the new character and they thought it was going to be bad enough with 9 main characters so why make it even worse by having 10 main ones? If they'd kept Kes, this would probably have meant that one more character would have been written zero to very few stories about and it was easier to let one go.
And yes, although I would have preferred ten main characters, perhaps Harry would have been a better choice. Not that I don't like him or anything but the fact that the actor had often been behaving like a diva on the set (thereby causing a lot of headache for the creators of the show) would have made it perhaps more acceptable to fans that he was let go rather than Kes.
Just guessing, of course.
I've heard Jennifer Lien say several times that it was just a matter of her contract not being renewed, which is a very common thing for actors. She said she had no ill feelings about it or to the powers that be.