Whilst it is not unheard of for Inquisitors to 'team up' on occasions,  I think it would be nice if we could play the companions as player characters in such games. The idea is that we could develop these characters with skills that would be more suitable to the members of an Inquisitors company than the main characters themselves. For example adding passive bonuses and, being able to 'assist' with those Investigation interrogations, etc.
Taking a step further if programming allowed, these companions could partake in the game and gain experience as npcs, in a similar manner that we  can apparently have guardsmen attached to an Inquisitor; even have the option for other players to 'hire' them, for their own games thus increasing the experience of the npc. Just a couple of thoughts.