Let's talk about logic for a sec.
In Chosen The First Evil says the line passes through Buffy. Who besides Cordelia has ever said the line passes through Faith? Marti Noxon did pre-Season 5, but Joss Whedon wrote the First Evil line in Season 7.
Of Cordelia or Marti Noxon, vs. The First Evil or Joss Whedon which ones are more likely to know how the slayer line works. And let's remember Cordelia was just guessing at the time, and it was in Season 3.
But wait the way the theory goes, all the mentions of the line passing through Buffy in Season 7 are mistakes. Who made them then? Joss Whedon who wrote Chosen? Are you telling me I shouldn't believe Joss? Are you saying what Joss says is a mistake?
Oh, but I almost forgot there have been a couple of mentions of a quote by Joss Whedon saying something like a slayer is like a battery or something, and this quote is supposed to prove Joss said the slayer line could only run through Faith. I don't know how many times I've asked for a link to this quote since rumour of it turned up a few months ago with a new member. No-one has been able to provide such a link. Do you know why? I have a theory. It doesn't exist.
Would you like to see what does exist?
https://www.buffy-boards.com/showthread.php?t=5934
I'll save you the visit to it, and tell you what it is. It's a post by a user from 2003, explaining his personal theory on how the slayer line is like a battery. Don't think that's the original quote. Fine. Search for the one by Joss Whedon then. I did. The only thing I could find was the message board quote above. Find that original quote, link to it, and I'll give you an apology. You won't find it though, because it doesn't exist.
So let's talk about logic some more. On the "slayer-line passes through Faith" side we have evidence from a Season 3 quote by Cordelia, an old pre-Season 5 quote from Marti Noxon, and a rumour of a mysterious Joss Whedon quote from a 13 fan who thinks he might have heard it somewhere, some time.
On the "Slayer line passes through at least Buffy in Season 7" side, we have three mentions of it from 4 separate characters, one of them written by Joss Whedon, as well as Beljoxa's eye's statement there is a "disruption in the slayer line".
So tell me again why Faith is the "logical choice". If you meant to say emotional choice, that's cool, but the "logical" thing just doesn't stand up. It lacks support.