At the end of the day I agree with you on this. But I think you overstate the case against Spike as Twilight.
First, Joss and/or Allie have said that S8 is something like 18 months after series. And Dawn has leapt to college age (which even at 18 months still has her as a very young collegiate). So S8 is definitely post-NFA. I think that's the whole reason to choose 18 months as the jumping off point. I don't think Giles was in the habit of assassinating rogue slayers prior to NFFY; the whole premise of that arc was that it was a very big deal to take such a step, but necessary in this case. I don't see any reason to think that salvaging problematic slayers wasn't SOP prior to NFFY. Dana isn't rogue per se. She's insane. There are lots of ways to develop the "vampires are real" reveal in S8 with the "we were in hell" developments in LA so that the timelines workout.
So I don't think there's a problem with Spike or Angel as twilight on that count.
How about the absence of plausible thematic? Here's a case for Spike as Twilight:
Twilight didn't have a problem with one slayer. He's responding to problems that cropped up as a result of there being many slayers. And he says it falls to him to do something about it. Spike has a connection to that transforming event. Buffy has the scythe because on her own account he gave her the strength to retrieve it. He was her right-hand man and confidant at the end. So he's a part of what went down. Before S8 started unspooling I thought it would be very cool if the guardians tapped Spike, the slayer of slayers turned good, to be the one to work to offset the inevitable bad repercussions of there beign too many slayers in the world. It would put him in opposition to Buffy in many ways. Anyway, that's available in the Twilight story line, since Twilight is not obviously wrong about the problems with too many slayers.
The statements about knowing the slayer well are also quite consistent with Spike.
But you are right that the speech patterns are off. It makes no sense that Riley of all people would work with Spike. Spike's wonderful, but he's not a leader. And one has the impression that Twilight is tall, and Spike isn't. If this is Spike (which is stretchy in the extreme), it's a future Spike or something like that. A very altered Spike. And maybe he's kept his identity secret from Riley, as well.
Agree that Caleb meets the criteria about the use of the term "girls" throughout Twilight's dialogue with Buffy; he knows that move (though Angel and Spike do as well). But do we have any foundation for Caleb caring about Buffy (as Twilight obviously does)? For him knowing her particularly well? Intimately well, even? And Caleb had a problem with any slayers, where Twilight's issue seems to be too many slayers. It'd take some work to move the cartoonishly black Caleb into the role of the interestingly ambiguous Twilight.
As of now Joss is going to have to close logical/narrative gaps somewhere. Spike is a dark horse. But I can't quite rule him out. I suspect one could make a similar dark horse case for Angel. He meets a lot of the criteria Spike meets with the exception that Angel doesn't actually know the real Buffy all that well, and it's not obvious why it would fall to him (unless that's part of his generic problem with thinking of himself as the major player in all things). The major objection to Angel is that it's hard to see Angel being available for a supporting role in Buffy's story when he's lined up to star in upcoming stories of his own.
Re: part 2 - Why Twilight isn't Angel or Spike
First, Joss and/or Allie have said that S8 is something like 18 months after series. And Dawn has leapt to college age (which even at 18 months still has her as a very young collegiate). So S8 is definitely post-NFA. I think that's the whole reason to choose 18 months as the jumping off point. I don't think Giles was in the habit of assassinating rogue slayers prior to NFFY; the whole premise of that arc was that it was a very big deal to take such a step, but necessary in this case. I don't see any reason to think that salvaging problematic slayers wasn't SOP prior to NFFY. Dana isn't rogue per se. She's insane. There are lots of ways to develop the "vampires are real" reveal in S8 with the "we were in hell" developments in LA so that the timelines workout.
So I don't think there's a problem with Spike or Angel as twilight on that count.
How about the absence of plausible thematic? Here's a case for Spike as Twilight:
Twilight didn't have a problem with one slayer. He's responding to problems that cropped up as a result of there being many slayers. And he says it falls to him to do something about it. Spike has a connection to that transforming event. Buffy has the scythe because on her own account he gave her the strength to retrieve it. He was her right-hand man and confidant at the end. So he's a part of what went down. Before S8 started unspooling I thought it would be very cool if the guardians tapped Spike, the slayer of slayers turned good, to be the one to work to offset the inevitable bad repercussions of there beign too many slayers in the world. It would put him in opposition to Buffy in many ways. Anyway, that's available in the Twilight story line, since Twilight is not obviously wrong about the problems with too many slayers.
The statements about knowing the slayer well are also quite consistent with Spike.
But you are right that the speech patterns are off. It makes no sense that Riley of all people would work with Spike. Spike's wonderful, but he's not a leader. And one has the impression that Twilight is tall, and Spike isn't. If this is Spike (which is stretchy in the extreme), it's a future Spike or something like that. A very altered Spike. And maybe he's kept his identity secret from Riley, as well.
Agree that Caleb meets the criteria about the use of the term "girls" throughout Twilight's dialogue with Buffy; he knows that move (though Angel and Spike do as well). But do we have any foundation for Caleb caring about Buffy (as Twilight obviously does)? For him knowing her particularly well? Intimately well, even? And Caleb had a problem with any slayers, where Twilight's issue seems to be too many slayers. It'd take some work to move the cartoonishly black Caleb into the role of the interestingly ambiguous Twilight.
As of now Joss is going to have to close logical/narrative gaps somewhere. Spike is a dark horse. But I can't quite rule him out. I suspect one could make a similar dark horse case for Angel. He meets a lot of the criteria Spike meets with the exception that Angel doesn't actually know the real Buffy all that well, and it's not obvious why it would fall to him (unless that's part of his generic problem with thinking of himself as the major player in all things). The major objection to Angel is that it's hard to see Angel being available for a supporting role in Buffy's story when he's lined up to star in upcoming stories of his own.