Can I "cheat" by having satellite, PSTN, cell phones, semaphore, smoke signals, sneakernet, etc. to allow the DCs to negotiate (perhaps randomly) which will consider itself the master? Then the non-masters could direct users to the master.

I guess this isn't a true "partition" and if we're talking about an internet backbone cable cut, it might go unavailable for some users who could not be redirected, but for the rest it is intact. While networking failures are to be expected, could I minimize my risk of a complete partition by sharing this status information? I suppose if we're in a cartoon end-of-the-world scenario where my 3 DCs drift out to sea on separate continents, I go unavailable, but at that point everyone has bigger problems to worry about.

If the PSTN, cell phone network, Internet, dedicated fiber link, shortwave radio, roads, and navigable airspace (drone, helicopter, carrier pigeon) between all 3 of my locations are severed, then the system goes completely unavailable, but at this point we're talking about a mass casualty incident, civilization collapse, or other situation where no one would be trying to use my system anyway. Medical records for first responders would have to fail to "eventually consistent" but patients can only be in one place at a time. Unless my system is the nuclear deterrent, does it matter?