Nope... Option 3 with them being dead is just cheap. Not effective narratively in my humble opinion.
I get very attached to my RPG companions and would rather they had something to do while not in my party, or if they die or leave, it should be because of the player's CHOICES having consequences. Not because of an arbitrary gate where the chosen party goes through and the rest just drop dead for no reason.
Sorry, but are you arguing that's not effective just with just your feelings? Implementation can be better, yes. But effectiveness lies in different part here - hoever you make them leave you can be sure no one will ask "why they are doing nothing?"
I argued that it's not narratively effective because companions leaving/dying should be dependent on player choices, not passing some arbitrary point in the game.
Wyll and sometimes Gale (depending on roll result) leaving the group because of player's evil path choices = makes sense in the overall narrative. "Why are they doing nothing?" isn't a question that comes up in this scenario.
Small group of 4 going to Moonrise Towers, meanwhile everybody back at camp suddenly drops dead because The Will of Larian says so? Doesn't make sense, unless they have a really, really damn good story explanation for that!
My feelings factored in, yes, but they will match others on this forum. I'm probably a typical, average casual gamer who mainly plays RPGs for the story and companions.