BioWare can't afford to let any squadmates die.

There can still be nuances and permutations, just not about squadmates. 
I agree on revealing it beforehand though

Because BioWare made all of these squadmates optional, it did not make sense to invest money in characters who might be dead for 50% of the player base.

Not only do I disagree with this, but I think it cost them money.
It IS possible and worthwhile to invest in characters who might die... Because it will totally shit load increase the amount of replayability for the WHOLE trilogy!
I mean, If I knew that Samara had a large part in ME3, I'd totally replay ME2 and take her instead of Morinth, just to see what happens.

If making sure character lived would replace possible squad mates in ME3, people would want to play ALL options! Lets say if Jacob survived in ME2, he'd replace James, but if he didn't, you'd get James instead... That would totally increase the replayability of the entire franchise!

That would require more money and resources to be spent, which Bioware didn't have. And likely won't. It's not a small investment.

corpusdei : yeah, he and Legion had big roles, along with Garrus and Tali (although they were ME companions too). The others were left with abysmal roles. They can't do what they did to Mordin for every previous squadmate.

That would require more money and resources to be spent, which Bioware didn't have. And likely won't. It's not a small investment.

corpusdei : yeah, he and Legion had big roles, along with Garrus and Tali (although they were ME companions too). The others were left with abysmal roles. They can't do what they did to Mordin for every previous squadmate.

I still remember all the complaint threads on the old BSN when Thane died, despite the fact that he told you in ME2 he was going to die regardless.

With mandatory deaths, then the developer controls what sort of combinations of personalities need to go forward into the next part of their story.  With ME2, because it was all optional, they had no control over that.  Therefore, they just couldn't write any of those personalities into the main thrust of their story.

None of our squadmates have the option to die in MEA and that's a good thing.

www.gameinformer.com/b/features/archive/2016/11/08/101-questions-and-answers-about-mass-effect-andromeda.aspx (Start at 4:27)

Why, you ask? The moment any squadmate has the option to die is the moment that character is no longer integral to the plot going forward.

Lets take every single companion of ME2 as a perfect example. If you chose, you could let the entire squad of the Normandy die. This required quite a bit of effort, from not doing loyalty missions, not upgrading the Normandy, and making sure to pair squadmates on the worst jobs that would get them killed during the Suicide Mission.

Now, at first glance, you might think this level of player agency and choice is great. However, from a storytelling standpoint, it's actually incredibly terrible. Here's why: Every single squadmate in ME2 largely became irrelevant to the plot in ME3. Miranda, as my personal LI, was relegated to a largely minor role with barely any dialogue and screen time. Because BioWare made all of these squadmates optional, it did not make sense to invest money in characters who might be dead for 50% of the player base.

We can also use Ashley as an example. Due to her being a potential casualty in ME1, if you agree to bring her aboard the Normandy in ME3, her amount of dialogue and interaction immediately ends (largely becoming one-liners and drunken stupors). It's really only during the first half of the game that Ash gets any kind of quality character development. But, it's clear that her potential death made her less of a priority than someone like Liara, who couldn't die. This is why Liara had the most character development and even the best romance scenes!

Sure, it's interesting and can provide new dynamics as well as moral dilemmas if a companion has to die. Unfortunately, the level of worth to that companion immediately dissipates as BioWare cannot write a character into the main plot who could potentially be dead. Thus, any potentially dead companion is creatively dead from a storytelling standpoint and no longer can really offer anything to the experience.

There's obviously no risk if none of our companions can die, but at least our favorite companion doesn't disappear into obscurity as a result!

They don't really need to - I didn't really have any problems with major/minor companion characters. The argument that "because character X can die, they can't develop the character" doesn't really hold water - there are enough examples throughout Mass Effect series to prove otherwise.

Saying "because everyone could die, BioWare doesn't have the resources to full develop every character (and their stand-ins)" would be more accurate... but is that a problem?

Come on OP, spoilers!