I'm curious what will happen if she is dead. As in my game, hehe. Nothing? Some repercussions in Baldur's Gate?
I gues the same that will happen when you kill Astarion, Shadowheart, Gale, or Lae'zel (who can be storywise killed in multiple ways by the way) ... i dont think i have seen any story way to kill Wyll, only when you attack Grove and he is not recruited, then he is one of defenders ... but level 1 so, no bigy.

I presume there will be some minor change in the future, just as if you kill Zevlor ...
Next in comand will simply asume his position, and the story continues.
My personal gues tho, is that we would need at least single Origin companion alive at end of Act I.
Bcs i strongly believe that their personal story will be our starting point for Act II.
But thats just me guessing.

Mercenaries are usually characters fully created by the player. Name, sex, class and so on... you create them in the character creator, exactly as your main character.
This sounds to me like custom characters ... wich was also confrimmed, but as far as i remember (and it is possible that im misstaken, its has ben some time) they were mentioned separately.

They don't have anything to say and don't have any story. They're just bland character you can "recruit" to create a fully or partially custom team.
This on the other hand would be exactly what i would expect ...
I didnt play DoS, but i heared there was Mercenaries aswell ... so if anyone could tell us how they were done there, that would be probably most acurate description.
The only game i have ever used any "mercenaries" if that is even possible to use for them, would be Diablo II. but nobody was extra talkative there.

But yeah, that is what i would expect ...
Basicaly void character that is only fulfilling role of desired class in matter of combat.
Still i believe even that would be (a little) better usage for Nettie than just left here in the Grove without any futher usage.

As i said its my personal "at least" or "the bare minimum" ... surely the more she would ne integrated to the story (at least story of first Act), and therefore the closer she would get to proper companion ... the better.

I admit it, it simply pisses me off that she is talking about how existencialy imporant is for the whole Grove to find Halsin ... and then she gives you vial of superstrong poison to kill yourself, wish you good luck, and go take care about some stupid bird.

I simply NEED to take her with me in search for Halsin, even if she would be just silent follower without any personality.