If they suddenly shift to a 6-person party - given that all encounters are presumably intended for 4-person parties - how can this not affect encounter design/difficulty? Surely encounters will be too easy so you'd need to rejig them? .
It's not that it can't", it's simply not important. Let it be MY problem if I'm fine playing "easier encounters", in the same way you don't worry if someone plays "Story mode".
I'd prefer the game to be balanced for my ideal party size? Yes. I'm all for a bit of challenge? Yes. I will still take the "six men mode as an easy mode" over being forced to stick with four characters, given the choice.
I'm not even making a random guess about "what I think I would like". I *already* played this alpha hacking a savefile to play with a full party of six (as it was already discussed in the past pages, but we are doomed to going in circles apparently) and it was a fucking blast. I had more fun than with any of my other three playthroughs.
The pacing of the combat was better, the loot distribution was better, having more people interjecting in dialogues and bantering with each other at any given time was better. The only thing that took a marginal hit was the challenge, but that's my problem. As I said, I'll take that over playing with a shitty restriction that doesn't enhance my enjoyment.