This is one thing that annoyed me in Fallout 3/4. The one-person party limit seems extremely small, especially compared to fallout 1/2 and most other rpgs where you can have 3-5 people usually.
Not to mention this drastically cuts down on the storytelling aspects in terms of the dynamics of all of your companions and their interaction not only with the player character but the other party members and npc's.
It'd be nice to have 2 other people + a non humanoid (IE dogmeat/robots).