I agree with points B,C and D. I don't think the companions need to be that shallow in a game like this. Voice over costs won't be an issue, so it all comes down to writing the companions, which I've always felt was one of the things Obsidian does way better than any other company.
Though I agree that all of the companions won't necessarily have to have a questline of their own. Just as long as there is bantering, shared momements etc. with every one of your companions (well maybe not with dogs and such). Though I guess everyone can't comment on everything you do. But still I would hate to see quantity over quality, I want both quantity and quality.