My pitch has grown a bit with further discussions! And I'm trying to pitch it in a way that makes for viable television, not just fanfiction.
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Just a a few notes about my pitch for a continuation that works with the real ages of actors and their availability... I should also note that Xander (played by Nick, anyway--Kelly might work for a flashback) is a character who could never appear in live-action again, so maybe he could be used as another event that contributed to Buffy's retirement besides pregnancy.
If the Shanshu and conception were directly post-NFA, any offspring would be 16 years old right now. IMO, if there were any plans to give SMG a series with her in a major supporting role, this just means that the space for how long between NFA and the Shanshu or how long Bangel got to be with each other widens for however many years it would take to revive the franchise.
I strongly believe that the best option for the franchise would be a back-to-the-suburbs story exploring age-appropriate Buffy facing motherhood, rather than trying to turn Buffy into a war general surrounded by nothing but subordinates (horribly alienating future for her) with a lack of equals or a grounded setting à la the season 8 comics. If you want to introduce the Buffyverse to a new audience whom you can't expect to watch 24-year-old shows until they're interested enough by the revival, you're going to have to ground characters in a relatable reality.
As for how a new Slayer would be called after deactivation, I firmly believe the line is through Faith now anyway, so it would just take her dying for a minute à la Prophecy Girl for a new Slayer to be called. I would definitely want Faith in the show!
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I feel like SMG's concern was less wanting to reprise the role entirely, but more concern that she'd be expected to play the same exact role in her 40s. This is giving her a role that fits a woman (and a mother in real life) who is in her 40s and is a major supporting role rather than he young lead whose story is being centered on.
As for the Angel situation, SMG might actually be more willing to return if she could beg DB to come back for perhaps an initially-limited role and the scenario is one I believe she'd actually support, as it fits with her preferences!
While it might seem that Buffy as a single mother retreads the original, Angel is obviously nothing like the Hank situation (not to mention Joyce and Hank being completely clueless), so the circumstances of the father would be quite different from Buffy's own situation, while also feeding into her own stated fears about her future.
This also brings up all the conversations in Bad Eggs, The Prom and the Chosen cookie dough analogy (children are mentioned again) to the forefront. Unlike with the other options, it was something that came up repeatedly. Admittedly, it was always by Angel due to his infertility and the human life he most desired; all of which ended up being an important part of *his* story.
However, a part of Bad Eggs that is woefully underrated is that Buffy was disappointed when Angel told her vampires can't have children. She immediately covers it up with a babble speech and then starts making excuses for why Slayers are unlikely to have that kind of future. Young Buffy did not disregard it because she didn't want children ever at all, but because the person whom she saw that future with was someone who couldn't have them.
Enter Nikki Wood, where Buffy learns that at least one Slayer was definitely a mother, which she was clearly surprised by.
That's another reason why I can see Buffy, if she got her hopes up with post-Shanshu Angel and conceived, would do anything to be a good mom by not being all about "the mission". She would never want her child to be raised without parents. And I think she'd be doubly sensitive to that, not just because of Nikki, but because of Hank leaving and Joyce dying.
Buffy also became surrogate mother to Dawn, who was made out of her (in a sense, she is her real mother), so Angel's situation with Connor actually had a direct mirror in Buffy's situation with Dawn.
But those conversations were also not just about wished-for children that couldn't be conceived, but also asking Buffy to think about what she wants for her future if she took out the belief that Slayers don't live long enough to have one.
This show would be the answer to what happens to a Slayer when she does live long enough to have the future she barely wanted to get her hopes up for before.
Buffy (ditto Angel) is the character for which this story actually has a ton of setup in the shows themselves. These characters talked about it! And the circumstances are really nothing like Joyce and Hank, even if the initial setup plays into both Buffy and Angel's worst nightmare scenarios about parenthood: being a single mother and not getting to raise the miracle child you thought you'd never have. That kind of bittersweet writing that shirks too-good-to-be-true wish-fulfillment is a cornerstone of what makes it a Buffyverse storyline.
If the daughter's family lied to her about their history to keep her safe and protect her from knowing what goes bump in the night (making them the polar opposites of Hank and Joyce in regards to knowing all too well--especially Angel's experience of being the worst thing you could bump into at night, rather than utterly clueless), that would certainly be a conflict. Especially if she found out in a particularly shocking way (say, prophetic dreams).
And if Angel (I'd like to imagine he has the company of ghost!Wesley and maybe Illyria and Spike) has been taken for punishment by Wolfram & Hart, it might really confuse her if she doesn't know that he didn't just leave or some other excuse Buffy covered it up with.
Wolfram & Hart would also probably love the irony of Angel getting what he most desires (to be human and a father), only to punish him with it by wasting his remaining years separated from all that he loves.
