It Would Escalate Really Quickly

Question: If the twelve Olympians had to give up their seats, at least temporarily, and had to choose a god to take over their seat in their absence, who do you think each of them would choose? Just a crazy alternate universe idea.

That idea is so crazy that I don't even know how to answer it!

Greek gods are just... just so maladjusted, guys, I don't even know what to do with them. They're so heavily invested in their own power and prestige that getting them to give up their seats seems almost entirely impossible to pull off (I suppose most of them might do it if Zeus ordered them to, but who's going to order Zeus around?). Then, when choosing "replacements", there'd be a zany carousel of choosing incredibly awesome people - because if you're going to fill in for Poseidon, you'll have to be the most fucking amazing sea god ever conceived of to come close, and he's not having some failure take up his mantle and let his job be done poorly! - and choosing incredibly inept people, because if you dare try to be better than Athena at her job, she will go completely batshit at your presumption and challenge. The concept of hubris in Greek mythology - the sin of pridefully assuming oneself to be an equal to the Olympian gods - makes nominating other gods to replace them insane. These are gods who regularly murder, transform, imprison and purge the family lines of anyone who dares call their ultimate power into question. There is no nomination that won't end in bloodshed and eternal vendettas.

Also, they're pretty goddamn condescending to pretty much every other culture they encounter, so they'd probably want to choose only other Greek gods - but there aren't a lot of other Greek gods powerful enough to take their spots effectively, but the powerful ones in other pantheons would suddenly become rivals deliberately trying to undermine their power, and we're back to square one with the screaming and the shapeshifting and the Vengeance.

However, as a purely academic alternate universe idea where things weren't so insanely insane, I'd say that it'd be fun to replace them with those gods who have influenced them the most, or been influenced by them the most. Zeus, Poseidon and Hades are almost certainly heavily drawn from the Canaanite Baal, Yam and Mot, and they'd carry over not only their epically huge ruling-the-world stones but also a great deal of sibling rivalry and infighting, both mirroring the Greek pantheon to some extent and possibly pacifying the three Greek kings with the knowledge that their rivalries among themselves would prevent them from making a united from against them when they come back to retake their seats. Hermes might hand over the mantle to Anubis, often syncretized with him as the psychopomp and guide of the dead, who would no doubt perform the task with equivalent efficiency (if less mischief). Dionysus might hand the reins over to Osiris, who had a curious crossover cult with him in ancient Egypt, while Aphrodite could be subbed in for by other slightly-insane sex-goddess bombshells like Ishtar or Astarte, both of whom probably lent influence to her character. Artemis was heavily crossed with Bastet, so much so that her influence succeeded in turning the Egyptian goddess from primarily associated with sun to moon, so the nights might get that much more feline. And Hephaestus was the go-to guy for interpreting Slavic myths about the smith-god Svarog, so he's inviting Titans to this party now.

Those without such close ancient ties would probably want to call in gods who were similar to them in function and powers. Apollo's status as a sun-drenched archer would make the Chinese god Houyi an ideal candidate to replace him, but his healing connotations might make the Hindu Surya more of a good fit (or Asklepius, if the poor guy were still alive!). Ravenous, bloodthirsty Ares might be stood in for by ravenous, bloodthirsty Huitzilopochtli, or perhaps by the Persian Vahram, still on his world tour of badassery. Demeter, as the earth and fertility mother of ancient Greece, could probably tag in Mokosh, the earth and fertility mother of the Slavic countries, and Athena as goddess of military wisdom has plenty enough in common with Anahita to swap out and see what happens. I'm not sure if you wanted to include Hestia, who was originally one of the Olympians before she gave up her seat for Dionysus, but if you did, she'd probably have the hardest time finding another fire goddess who was as chill as herself; she might have to settle for Pele or Oya, and life might get a whole lot more dangerous for everyone else.

Of course, if you run the Roman gods as separate from the Greeks, they're known experts in impersonating the gods of Hellenic Greece. In fact, you could claim that ancient Rome's religious run was just this kind of experiment - the Greek gods taking a vacation to watch with amusement as some other pantheon tried to be them.

But seriously, everybody's going to end up dead at the end of this story.