I personally would prefer fewer, but well written and well voiced companions that are an integral part of the story (like we have now) rather than heaps of poorly written companions.
IMHO the writing and voice acting in this game is EXCELLENT, and that requires quality, good (well-paid) actors, and time to get it right. They're already taking their time with the game as it is. It would be very, very hard to maintain that same level of quality across so many companions, and tie them in to the main story. If some of them were noticeably shallower or somehow lesser than others, I'm sure there would be more complaints...
I understand where people's wish for more and more companions is coming from (to cover all the classes so you could balance your own party however you want, to cover more alignment options for how you like to play, etc) but in terms of game design and the sheer amount of time, effort, and paid actors, it just doesn't seem feasible.
It could be SLIGHTLY more feasible to have more if at very least there wasn't the need to write these companions from multiple perspectives, according to having them as companions or player characters.
That's the sort of stuff that tends to inflate costs significantly. And I still question the assumption that the pay off may be worth it.
In fact I openly doubt it.