How did you manage to get there 5 ppl? O_o
The UI is ready for an increased party size.
Mods already allow to play with more characters in your party because you know, that's something many players love.
I know that, i was hoping for some clear and function 6members party mod, that i just install and play.

Since all i found so far was only "guide to altern the game so you can play with more characters" ... and im honestly too lazy (or lame? strike out what does not apply) for that. :-/