
On the subject of limited Collectors Editions, good. It makes me feel proud to have been smart enough to order one as soon as I heard they were selling out. If someone calls something limited, you don't assume it's going to be around for all of time. Just a heads up. Limited ie exclusive. No one to blame but yourselves. Next time pre order right away, it costs 5 dollars and a quick trip out of the way to save yourself from whining on the internet at a limited game with limited supplies *GASP* being sold out. Who would have ever thought. Perhaps the Skyrim Collectors Edition just wasn't in demand as much. Given the lack of content and price tag I wouldn't be too surprised. It was still some nice content, but definitely not at a price range a lot of people are happy paying for.
I've seen more spoilers of the story line, there's no way in hell this game has any cut content. I don't think the squad mate is all that critical to stopping them really if what I've seen is true. More of an oh neat look kind of thing. It will help, but is definitely not critical or the defining factor in any way. Or if it does have cut content it might be so the game can fit on the discs. There's only so much room. And people would whine like the Wardens Keep DLC if it was exclusive for a little while for the Collectors edition. So why not release it? It doesn't make any sense not to. ME3 is 2 discs on Xbox, I doubt they could fit the content on the disc. A. Either a limitation of the disc means if you want to load the squadmate you would need to load disc 2. Or B. There simply isn't enough room.
Sometimes companies do cut content, but I think this is the one time I can officially say they aren't.
Edit
I doubt the companion will even be all that fleshed out. Think Kasumi or Zaeed from ME2. If he was that critical he would be in the main game, trust me. I've seen some of the plot. The squad mate ranks as a blip, not even a big one compared to some other squad mates from previous games.