Any ghouls or zombies in the Betweenlands should attack villagers, like vanilla zombies

I somewhat agree on the grounds that zombies hate where they [might have] come from and swamp hags are the closest betweenlands equivalent. It falls apart a bit when you consider that zombies did not come from villagers but ... whatever ...

They could retain some kind of hate if you consider them to be a reborn undead but I'm not seeing the lore for that. On the other hand, why should villagers (and not players) be safe in a corrupted dimension? Much like an immune system, perhaps swamp hags should attack anything "unusual"? Thereby providing a consistent mechanic.

If you just want a swamp hag mob that attacks villagers, you can make one with customNPCS.

But... we don't have any ghouls, nor any villagers in the dimension :P
Do you mean mobs like the Swamp Hag should attack regular vanilla villagers? (If so, why? They don't ever naturally meet)

Closing, these mobs never naturally meet, as Cyber said.