Some random thoughts on things I've seen posted here lately.
I'm not sure if we will have them for Act 1, but Larian did confirm they are going to have some kind of "hired mercenary" system for basic class access without forcing players to use the Origin companions.
I "believe" last we heard was 8 Origin companions for release. The remaining 3 possibly already known, I won't say here. While I personally am not a fan of the Origin companions idea overall, I would like to see at least 1 per class if they are going that route though. Hired mercenary's may be able to be custom built for max potential but lack the side quests and extras that fully developed companions come with(Origin or not). I'm generally always for more options.
On "repeatability"... I'm sure someone can call up the exact statistics and prove me right/wrong whatever, but I believe I can safely say most people don't even completely finish a single play through of most their games. 4 or 6 players per group at 8 Origins means you need 2 runs at least regardless to see everything.
As to the OP 4 v 6 debate. I believe some of the complaints elsewhere about classes being more diluted and generalized, ie everybody has bonus action stealth/can use scrolls/etc are directly related to the decision to go with a 4 player party coupled with not wanting to "force" multiplayer players into a "last guy to join has to play the healer" type situation. A party of 6 means you don't NEED to min/max quite so much and can afford to try adding characters who maybe wouldn't be quite so optimal.
