Sorry for the delay in response - my mother decided that between my assembling my Christmas present (a LEGO "Dumbledore's Tower" set), and Dad putting together the LEGO Hogwarts Express, there was too much Harry Potter stuff in the house, so as it had been a few years, it was time to re-marathon the movies . . . Which really only spurs my impetus to keep going here, even as it eats away at my writing time. 

Originally Posted by
Arbitrarity
Or you can have some mix of characters-as-Servants and characters-as-Masters, though I suppose Ilya wouldn't stand for Shirou being Archer-ified.
Or becoming a Lesser Grail, herself.
Feels a bit weird since you
just did
Anarchy, which was loosely in the same setting.
Agreed, but this one I could play a bit straighter, since I wouldn't need to deal with Scions or Exalts.
It certainly has the most obvious support for introducing a wide cast.
Yes, and it involves a team effort, unlike most such stories in the Nasuverse - less hand-waving necessary on my part.
Extella doesn't really have 1v1 deathmatches, unlike
Extra. It's a Musou-style, hack and slash, big battlefields, territory control.
This is true, though it does canonically follow on from (a version of) EXTRA's plotline, which is the primary issue.
The original plot is very Hakuno-specific though, and would require adaption.
Yes, that's the other major problem . . .
I guess you can split the Seven up in a similar sort of way (Red/Blue/Green), which could work? Throw Galen and Luna with Altera, mix up the rest.
. . . And now I'm seeing Luna as hosting Jeanne d'Arc - I'm not sure whether to laugh or feel sorry for the Ruler.
Unless I bring in Extella/Link, anyways - but that reuses a lot of story beats, anyway.
Depends on where you want to drop into it
. Arguably, you could make Ilya and Shirou the
parents?
Fate/kaleid liner Prisma Ai . . .? It might work . . .
It seems a bit crowded to drop everyone in, but might be the right scope in the Ainsworths' world.
True - though that world is also insane, in a lot of ways.
Haven't read this yet, so fairly unsure. It seems quite complicated, but also of a scale that could work.
Exactly. The only thing really going for it that I can think of is that at least part of the plot revolves around And as that is an element I've brought up in Trinity before . . .
I'm assuming that should have been translated as "Preservation of Mystery".
Yes - which makes it painful to hear every time they use THAT. 
Also not really sure about this one with the wider cast. You're thinking of putting them on opposite sides, and... yeah, that might be a good way to fit the cast.
It'd at least be a place to start . . .
Depends on how you want to do it. You can just imply a lot of the story if you drop them in later, or make it more of an event than messing with the main story. Though now I'm imagining them as the Crypters, which would be... huh. I'm not sure I understand enough yet to say whether that makes sense, since I haven't read LB6/7, but that could be an interesting perspective.
It would be different, at least - and possibly more amusing if Ilya was the seventh, and Galen was the "Foreign God" . . . 
Dead Apostles exist, but it seems like a much harder thing to deal with in a Fate or Tsukihime world.
Yes - which is a major argument against this (see previous note about "crapsack world.")
Arguably, you might be able to weaken how powerful the thirst is within a Fate world, but their current solution may not suffice.
The remake has a few more degrees to Dead Apostles (literally) - I suspect she'd be a Stage IV . . .?
There's also whatever Consort Yu is doing.
Plot twist: ascending to the Throne renders Hermione as a human Caster, because her most popular epithet is "The Brightest Witch of Her Age" - with the possible drawback being that Servant Hermione Granger's background is drawn from the Rowlingverse canon . . .?
Being in a virtual world solves this, of course.
This is true.
Politics makes me wonder about
Case Files, but it's ruled out due to the lack of Grail War, gotcha.
Well, that, and that the Grail War that does involve it would involve crossing Shirou and Ilya's own timeline again . . . Once more - if she winds up being a twelve-year-old again, she will NOT be happy . . . And she's liable to have Herakles around to express it with. 
I can sort of visualize a few of these, but others, I might need more specifics. Prisma Ilya could be interesting exploring some of those parenting/guiding themes.
This is true - though moreso in Illyasviel's world than Miyu's, probably.
Extella could be a very short crossover, if you felt like doing that.
Perhaps - on the other hand, I'm constantly writing things longer than I expect to . . . 
[
QUOTE]I'm giggling a bit about the idea of putting the Seven in the Crypters' spot;[/QUOTE]
I can fully understand why. 
only one that seems really tricky is LB4... maybe a straight Neville/Luna/Ginny/Galen/Hermione/Shirou/Takara?
I'm not sure I catch your meaning with that question?
Might work better as snippets than actual long-form idea though.
True . . .
I'm not sure I'm more enthusiastic about these than what you're doing with Alex or Persona 5 right now.
Good to know, and thank you.