I think I would have liked it if someone HAD to die, like in Mass Effect 1- it was a surprisingly hard decision in the first one of who to let die (at least for me)
The idea that I came up with was that, when The Collectors launch the surprise attack after you get the Reaper IFF- that your next 'mission' involves you bringing your squad with you, but having to leave one person behind for a problem on the Normandy upon departure.
When the Collectors attack, the squad member has to fight to escort Joker through the ship.
Barely succeeding in getting Joker safely through, it comes down to whether that Squad Member is loyal or not.
If they are loyal, they are overwhelmed and taken with the Cerberus crew.
If they are not loyal, they are killed by the Collectors, or a Praetorian (etc)
This then adds either the urgency to rescue your Squad Member alive, with the crew- or to avenge their death with violence.
Additionally, this adds another level of weight to your decisions to other parts of the game, besides the End-Game section. You might pick your best, most loyal squadie to stay behind, out of trust, then frantically rush to get them back from the Collector Base, for their safety- and because you've used them in combat through most of the game, so combat literally FEELS different, harder. No matter the outcome, it also brings the feeling of remorse, knowing how things can really get FUBAR, and helplessness that Shepard's orders, which have gotten everyone so far, suddenly went so wrong and endangered one of the core crew members. Not to mention it builds up more hate and antagonism for the Collectors, or Harbinger, that keeps saying how he will 'hurt you' whenever you fight his avatars.
Not to mention that the squad member COULD be rescued with the rest of the crew- so doesnt interfere with that whole No One Left Behind achievement stuff.
P