I think the main reason why we're on short supply with down to earth companions, or "normal" people, is due to the fact that Larian seems enamored with a grimdark setting in their games, where people tend to be somehow creepy and/or fucked up beyond belief. The world of DOS2 was pretty grim, but at least there was more humor in the world(even the narrator VO was less malevolent), you were less traumatized by your captors, and it was easier to ignore/miss the "let's drink koolaid with the doomsday cultist" -plotlines at play.
Sadly, I can't see how a upbeat character like Lohse, Isabela or Varric would even fit in all this as an origin companion.
If what the dataminers say is true, then we will get Minsc. A friendly and often silly absolut hero who takes orders from a hamster. Even having his witch killed before his eyes did not turn him into a dark figure. It made him a bit more unhinged, but since it was an EVIL WIZARD who did it, his solution was just BUTKICKING, FOR GOODNESS! .
BG2 was dark, with all the torture and soultheft, but this guy took the dark setting and shouted light into it.
I am certain he will do the same in BG3.
He was depressed after fighting Strahd and realising that he has no chance of winning against this evil, but he even recovered from that.