I know that this is a scratch, but I wanted to ask this; I'm not sure whether this will be answered or not but... Ehh why not.

Is there a concept where Killigan is adventuring alone? Like maybe he met his team members on his journey but decided to go solo.

Oh, and could this concept be considered for addition to the game in the future?

...Uh, that's a fun thought experiment! But extremely unlikely it'll be considered for the game in the near future, since, y'know, it'd be rewriting the whole story.

Heh you're totally right that making that would be like building a whole new game, but I can't help but still think it would make a cool special mode or something... But from the start I was very satisfied with this game with many wonders in it that we haven't seen yet so don't worry.

Maybe my first question early is a bit complicated so let me clarify: Did you have that concept in the past that you had to choose between it and the current game concept?

And now here's my new big question: If that concept had been used, what would happen to Killigan throughout his adventure? And what would happen to everyone else involved with him?

The concept's always been for companions to join Killigan on his journey, so unfortunately, I don't really have a concrete answer for your latter questions! It'd be a much lonelier adventure, for sure. And much less fun or entertaining to write about.