I recently downloaded the Unfinished Business mod for Solasta just so I can play it with a party of six. Wow!! What a huge, huge, HUGE difference it has made in my enjoyment of that game!! And all the encounters have remained just as challenging as they were before, because I don't min-max in creating my characters and am running with an ecclectic gaggle of under-optimized characters that are built for my personal fun and enjoyment.
I simply cannot envision any scenario where I would be willing to play BG3 without being able to have my party of six.