How to edit Homeric hero trait

Hello everyone, I have an Idea for a Mod of Troy TW and I wish to ask if it is possible, and if it is how to do it.

I love Troy; it's one of my favorite Total War games. However, ever since the game came out, I've always been bothered by immortal heroes. I can understand why they added this feature, because if you play as Achilles, you want to face Hector at some point, and this would be impossible if Hector gets killed by the AI in the third round. Also, if you lose a battle with your main hero playing as Odysseus without having Odysseus survive, it doesn't make much sense.

This bothers me because death is one of the main themes in the Trojan cycle. We all remember the deaths of Achilles, Hector, among many others. It's disturbing that we can never have the feeling of having killed our rival.

But I have an idea to try to solve this issue: a mod that would make all the main heroes immortal while their factions are independent. However, if they are part of a coalition, they would lose the "Homeric hero" trait. So the characters would not die at the start of the game, and at the end, you would be able to kill Priam's children one by one or save Troy by defeating the main Danaean heroes.

Would it be possible to achieve this? If yes, how? I really want to play this version so much...