This can already be done without mods. A Mod to expand party size does improve the experience just launch the game without the steam launcher from the execute file multiple times. Running the game without the companions takes away from various different story line pieces. You lose out on gear quests ect story arch ect without having 2 companions for most of the content even doing multiple play throughs a lot of encounters up to 3 characters might chime in.
You don't loose out on anything if you switch around your party for the various quests. For anyone playing their first playthrough I would not recommend using a full party of customized companions, though. But for secound, third etc. playthrough, you will know who to bring for what, and will not miss a single thing. You will just have far more fun, because you can add much more of your own RP to the game, which personally to me, is what playing a cRPG is all about.
