The problem with that idea is that it's not universal for all Shepards. Aside from practical concerns like it doubling the memory budget by having to record the dialogue twice, what if you're playing a full on renegade that doesn't feel at all bad about the loss of Kaiden (I know I didn't!) It also risks alienating anyone who hasn't played the previous games as they'll have no clue who that person is, nor why they should care. Plus of course this would place that particular character's death as "important" over and above anyone else who may have died since in ME2 & earlier in ME3, which again is not universal to all Shepards.
They spent a lot of time in the game establishing the recurring dream and what it means to Shepard. The kid is just a symbol. Indeed, after one of the dreams (the second one I think?) Shepard can tell Liara that she was thinking about whomever died on Virmire.
If you're a Renegade who doesn't feel bad about killing Kaiden, why would you care about a kid you have absolutely no connection with? If Shepard is worried about humans dying on Earth, why wouldn't she care about deaths among her own crew?
Because no version of Shepard is a total socio-path? Like I said, there a difference between letting a comrade "die with honour for the cause" and watching a civilian get murdered.
I mentioned 'Schindler's List' before and IIRC that girl in the red coat is supposedly based on a real recollection of the events. Why amongst the piles and piles of bodies did that one suddenly mean more? It didn't really, it's just something amidst all the horror that can jump out and can stay with a person forever.
Had Shepard not see and spoken to the child then he might not have made such an impression when he died. Indeed, Shepard probably wouldn't have picked him out of the crowd before his shuttle blew up.
It's not a logical thing, it's an emotional thing.
Kaiden/Ashley work precisely because it's the first "major" choice the franchise forces you to make. You can get out of killing Wrex, but you are forced into a no-win scenario that even Kirk couldn't worm his way out of on his best day, so it's something that's universal to all people who have played the three games.
No that's precisely why it wouldn't work. The dreams aren't about no-win scenarios, tactical decisions, sacrifices made in the line of duty or even personal loss. It's about guilt, it's about helplessness, it's about responsibility and fear at a very deep, almost primordial level. It's not about people that *have* died but people that *are* dying right at that moment and are still dying because Shepard can't do anything to stop it.
The boy only says two things: "everyone's dying!"
& "you can't help me."
*That* is what's plaguing Shepard's subconscious. Not the words, or the messenger but the basic truth. Everyone is dying and you can't help them. I'm sure I don't have to explain the symbolism of being lost in the woods, whispers of the dead or the ever increasing number of shadowy figures.
Replacing all that with just Ash or Kaiden would utterly cheapen it and wouldn't provide anything in the way of emotional depth to Shepard's story.
As for new players? I don't think they would care about the story anyway.
No game designer worth their salt would ever approach an RPG with *that* attitude and I'm glad they didn't in this case. If they player doesn't care then *make* them care!