We'll have to wait and see how it works... lots of "if" actually as you said. One thing is not an "if" : I'll ask for an official party of 6 until the end but of course in a positive way and trying to find solutions (solutions from a random player that is not a video game developper).
I don't really like mods. I like playing the official version of a game and I'll try to convince Larian that this could be a great improvement for their Baldur's Gate game(s).
Wait and see on that point. Let's play the game first.
I agree in that yes there are a lot of ifs, however he did say in his own words in an interview that a mod would be "easy". So, if they added it it might not be too terribly hard to do. How to balance that is up to them but doesn't have to be rocket science imo. More enemies generally works well. (Which would simultaneously make level progression about the same.)
I'll keep politely asking for 6 as well. They know a lot of people want it. Those people might not be the EA players but they WILL be paying customers all the same. I want to play the finished game so I wont be playing EA. Like Maximuuus I don't really like mods either. I like options being in the core game itself, mods tend to be glitchy or have other downsides.
Also while it's cool they added those streaming features, for the vast majority of people who aren't streamers.... that's just a feature no one is ever going to use that who knows how much effort and time went in to.