Meanwhile, I'd also pounce on the "Ontological Alternatives" chapter there to ask a slightly unrelated question: Regarding the "fourth option" there, has anyone ever tried to analyze a world ontology where, unlike here, particles can belong to multiple different worlds according to some kind of rule or per-particle basis? e.g. Instead of having a particle belong to World # 872 as an elementary property, which lets it only interact with other W-872 particles, it would have a set of "keys" where any other particle that also has at least one of those keys can be interacted with, while that other particle might have a slightly different keyset and thus be able to interact with a third particle "located" right next to the first one (insofar as position of two non-interacting particles is relevant to the second one in question)?

I realize I'm throwing ideas around while having no idea at all what I'm talking about, but at the same time from where I'm sitting it feels like all the "sides" of the QM interpretation debates always share a humongous bag of uncontested assumptions. Namely, assumptions about pesky details like "position" being a necessary, elemental and fundamental property of particles.