I know the game support having a full party of four characters. The multiplayer allows four players to play the four characters, (i.e., Lucas, Anjali, Reinhart and Katarina.) If a player leaves the game, the AI will take over the player's character; effectively, it's like playing as a main character with all three companions active at once. So the support for four characters is built into the game.

However, the single-player mode disables multiple companions. So a solo player can have only one companion at a time. (I hate it when game removed/disabled a built-in feature from single-player to add "value" to multiplayer.)

Is there a way to enable multiple companions in the single-player game? A mod? Hack? Tweak?

..I think it has something to do with the way they've balanced the encounters. If you don't have human players, things start to get a bit out of hand just with three players, even on normal. Get stuck with two team-mates in the equipment screen during a boss-fight, and you're sort of not going to do so well.

 

Can recommend playing it online, though. Much more fun than I thought. Screen zooms out a bit, encounters become pretty impressive.. that sort of thing.

I do not play any MMO or any sort of online or multiplayer game.   That just how it is.  So thanks but no thanks.