"Unbalanced difficulty and frustration will stop them. Is it so hard to understand, that there a lot of people who liked NWN1 being centered around sole PC, who only bought OS2 because they could play it with only one PC? People who like parties may want 6+ PCs, but they will still be happy with 4. People who want to play with controlling only one PC won't buy and enjoy a game where they will feel handicapped playing that way."
But again, play it solo or with party of 6. Use proper XP split and it works. You play solo and gain 4,800 XP. You are now 1 character at Level 4, going on to 5. You play party of 6 and gain 4,800 XP. Split 6 ways, you have 6 Level 2 characters. Same challenges, same difficulty because 1 Level 4 = 6 Level 2's.
So, why not allow the game to be played with up to 6 party members so if you want to solo, you can, but if you want a party of 6, you can also?
This doesn't work with DnD system. 1 level 4 =/= 6 lvl 2s. Also in the endgame you hit content designed for 6 characters at max lvl while you only have 1. Try playing Pathfinder or BG2 with a casual not crazy min/maxed character even on normal difficulty without cheese, it won't work.
What are you talking about? Where do you think I got that from? That's exactly how D&D works. It is the D&D system. When you play D&D, if you go up against enemies and the DM awards you a thousand experience, that thousand experience is divided amongst the number of characters in the party. So, if you have four party members, they will level up much faster than eat party members, because you are giving more experience to each individual character in a party of four. So I can play the exact same campaign with four players as I do with eight players, but by the end the campaign with the four players will be higher level than the campaign with the eight players. I'm not entirely sure you fully understand how D&D works.
And it's all about how they implement things in the game. Sure if your solo playing you're eventually going to level cap towards the end. But I don't think that anyone expects that this game should be built based on a solo playthrough. This is a D&D game, and D&D is never meant to be played solo. It is meant to be played as a party of adventurers traveling together, a group of friends. That's why we are fighting so hard for a party of six. Parties of six are a classic for D&D.