I'm inclined to adopt this. Clear guidelines help prevent arguing and uncertainty. These do a good job of capturing the unofficial tendencies that already govern page creation.
However, there's an obvious problem: some "characters" cover multiple pages. This policy would imply that pages like Noelle's would be merged into their cape identity pages. It makes sense, but it does mean those pages would have to be marked as containing spoilers.
One page that's already like this is Shadow Stalker. Her true identity is a major spoiler. That's kind of a crummy page, though, so maybe it should be re-worked.
Taylor Hebert also kind of does that, but would be renamed "Skitter" under this policy - is that ideal?
One possibility would be to rule that separate identities get their own page if they're a major spoiler, or if there's enough material for a separate page. Do we want to separate pages like Taylor Hebert and Defiant, maybe even Flechette/Foil? (Hijack, now, I could see him having a separate page with little difficulty.) The tab system, which we didn't have when most of these pages were created, might help with this.
Should we be including "The" in character names? Siberian, for example. It's inconsistent in the text, but we do do it for some teams - and it's not like we title Danny Hebert's page "dad" just because he's called that sometimes.
Guidelines for characters without names.
I'd suggest something like:
The title of an article about an unnamed character should use the following
The name given in the character tags, if any.
A bullet point that justifies Abaddon, somehow? I mean, never called that in the text, clearly not an in-universe term, but even Wildbow uses it.
If nothing else is possible, a descriptive title (e.g. "Unnamed Sniper") may be used, ideally one from the text (for example, "the woman in the suit" was used for Contessa before her codename was revealed.)
I should point out that the examples at rule six aren't exactly good ones. March (Gold Coin) is generally called Minakhm, and Leister the Protectorate member I can't find in any text except a spreadsheet :/
About rule 2: I'm in favor of add 'The' to names (I wrote it differently here because I wanted to fit it with current policy). The Siberian and the Simurgh are called that way because it dehumanizes them: It actually says a lot about the character.
I like your expansion on the nameless characters.
About multiple pages per character: How far do you want to go with protecting people from spoilers? Because right now pages are also being removed from navigation templates, and I didn't even realize there were multiple pages until I stumbled onto Echidna by accident.
A wiki should have clear, accessible data. It's why wikis are made. It's possible to have this and still protect against spoilers, but not how it's done now.
On the Abaddon point: other wikis have article based upon conjecture and say so the same can be applied here. When we finally get around to working on the O'Daly page we can include a similar piece basing it on conjecture.
Keep Taylor as is given her protagonist status, separate policy for characters who have major spoilers as part of their identity. Knowing who Noelle or the Siberian is before major reveals would impact someone reading of Worm.
4. The title of an article about a character not named in the story should be their name according to some other canonical source, if any. If there is no canon name available, a speculative name may be used, ideally based on references to them in the text.
7. Characters who are arguably the same person, such as the Siberian and her creator, or the different Butchers should only be given a separate page if there is sufficient material for it. Characters who are inarguably the same person, such as Flechette and Foil or Armsmaster and Defiant, should never be given separate pages.
The page Taylor Hebert is an exception to these rules, as she is the protagonist.