For me, creating own characters for my party would not be interesting, because I like the interaction/dialogues with our companions very much. I like to get to know them better with each dialogue and find out more about their backstories/character.
But I would like if there was an option to create own companions for players who prefer their own custom party, too. Different options for players with different playstyles/preferences are always nice.
Concerning the companions:
I am quite sure we have not met all future companions yet. I found this interview with Swen Vincke (Updated: Nov 10, 2020), where he mentions that not all possible companions are in early access yet, and I do not think that this has changed:
Link to the interviewA quote from this article:
“There's been a group of people complaining about the fact that the companions are snarky and they have to have an opinion,” Vincke reveals. “But we’ve only put the ‘evil’ and the ‘neutral’ ones out there. We haven't put any of the ‘good’ characters in yet, so I think that will balance that.
Personally, I like the companions we have met so far - and I am playing helpful, "good" Tavs. If these are the "neutral" and "evil" ones, I am very pleasantly surprised. I am very glad they are no stereotypical, mustache-twirling villains, but complex and even sympathetic characters. I could imagine that the player could maybe influence them in one direction or another, and it would not be out of character, since they all are very nuanced characters, in my opinion.
I would like to write more about the character writing in BG3 (which is think is very good), and our companions, but I will do this in a seperate thread (when I have more time), since I do not want to derail your thread.