This has happened already. Sort of.
https://youtu.be/hlfgp4aS_A0?si=KcyRc_E4UK8BMh53
SoV had a LOT of random scenarios for characters dying, including a lot of ending changes, some unique post-battle dialogue for characters if their friends/relatives died, and some unique plot changes like that one.
That game rules. They put so much love into it. I'm really sad that its sales were a bit whatever.
https://www.youtube.com/user/dotsdfe
I make Fire Emblem videos. Sometimes.