You haven't seen
this mod and
this guide? Also, Larian
patched the UI to improve the experience when that mod is installed: "Scrolling through more than four characters in the character-sheet UI now looks good and understandable."
Yes, I saw it, and we were talking about players in custom campaigns, with a GM. Not the main story. So 5 players playing the main campaign and 1 of them has to be a henchmen is the same workaround the modders did in the first divinity. But in Larian they programmed 2 more player slots (with their correspondant UIs, character creations and stuff) so expanding the player limit size for custom campaigns CAN be done. And I'm not the only one that finds this frustrating, in the first game it didn't matter, because you could only play custom scripted campaigns, but now we have a GM mode...but not enough room to play with our friends, and that's a huge problem for everyone, you can browse the forums, LOTS of people are asking for expand the player limit for GM campaigns.