I like the shared 6 roles for score generation. It provides randomness that can be fun, but avoids to party strength disparities that sometimes result from die rolling. But I've never been a fan of 100% random score assignment. IMO, this leads to too many unfun characters. I would suggest the following modification:
Each player roles a d6 to decide which score goes in which ability. But, the player gets to choose which stat they are rolling for (i.e. first I'm rolling for Wis, then Str, etc). Also, at any point in the rolling process, they can pick one of the remaining scores and choose which stat it goes to.
This allows the player to avoid any really undesirable combinations. "A 16 in Str, a 9 in Dex, and a 7 in Int? It looks like I'm destined for a melee character, so I better but the 14 in Con" or "I just rolled a 9 in Wis and 7 in Int. I don't want to be a sorcerer this game, so I'm going to throw the 11 in Cha."
