Yay, I love Big Crunch. BC is such a tasty sugary addictive treat. It generates lots of black holes in the (re-)collapsing universe just like Chocolate Frosted Sugar Bombs generate lots of black holes in Calvin's tooth enamel.

I think I mostly agree with you, loosely, that we could be in a BC cosmos but I also think it's not great science communication to say so because "could" is doing a lot of work there. :-)

Let's start by ignoring the fact that all the new z > 11 (!!!) galaxies JWST is spotting lately do not seem to be rushing inwards from the horizon[*], because I think those observations will kill (inertial) BC dead real soon now.

Expanding R-W gives rise to congruences that are incompatible with collapsing spacetimes, and those congruences are observed (e.g. the timelike geodesic congruence of COMs of galaxy clusters; the CMB's null geodesic congruences; this motivates the use of FRW dusts).

Collapsing R-W is plausible, since the Friedmann equations still work there; collapsing spatially flat FLRW is enough like Oppenheimer-Snyder that it's not worth calling "not a black hole" outside an academic context. I think at best we can say that maybe the expansion reverses at some point, and then try to work out whether evidence strongly disfavours that point being in the past. One would probably start conventionally, trying to measure the critical density by non-geometrical means (since the geometrical approach is pretty suggestive that recently (z < 0.1) parallel lines will stay parallel or diverge). That leaves coming up with some notion of quasilocal mass and counting it, but then I think you're not going to make much progress without a better understanding of the dark sector. Big project, many previous attempts (some high-profile), none especially satisfying.

Now you have me wondering how one deals with the Raychaudhuri vorticity tensor and other terms that would oppose (re-)collapse. Where does all the angular momentum within large galaxy clusters go? Hierarchical BH mergers probably can't be the whole story. I'm not sure we'd worry about that until well into the (re-)collapse, but I think we'd already have to look beyond the FRW dusts. (One would also have to overcome opposition to (re-)collapse from a negative trace of the electrogravitic tensor thanks to a CC-compatible DE. "DE undergoes phase change" is something I'd buy as an idea. Otherwise I think observations from Chandra/ROSAT (data in Vikhlinin et al., 2008) were a fatal problem for BC and big rip).

Ultimately I think we end up in the land of "something about the accelerated expansion would have to give" and speculate wildly against the trend. Taking that path seriously seems like a recipe for frustrating tension headaches.

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[*] the premise here is that BC should look like the actual expansion history under time reversal, and thus we'd expect to find the most distant galaxies brighter, smaller (because we reverse the angular diameter turnaround), and bluer than they are turning out to be.

P.S.: "In order to recognize an event horizon you..." should read Visser 2014 https://arxiv.org/abs/1407.7295

P.P.S.: Yes, "someone" could already have focused shells of radiation on our solar system such that we are already inside an event horizon and don't know it. Somewhere someone diagrammed a Kugelblitz spacetime with that in mind, but I don't seem to be able to find it, and am not sure I trust my memory that it was fairly rigorous (ignoring implausible initial conditions). It wasn't video so it's not the PBS Spacetime "Escape the Kugelblitz Challenge". That's not only very far from rigorous, it's pretty consciously silly. (The challenge should ramp up the mass so that the settled horizon would be trans-Neptunian, and ask whether humanity can engineer anything at all which could escape).

P.P.P.S.: None of this is about falling into an astrophysical black hole like Sag A* as opposed to already unknowingly being in a "black hole".