Nuance of 在る for a person in this song


In the song "my code" by GARNiDELiA, there're these two lines:

> 噛｛か｝み締｛し｝めた痛｛いた｝みも 消｛け｝せない傷跡｛きずあと｝も
>
> 私｛わたし｝が私として在｛あ｝るために

I understand what the second line means, and I've read other posts on this
site about ある being used for people in some cases, but I'd like to know how
the feel of this line would change if いる was used instead.

Also, everything I've read specifically says 在る with that kanji is used for
inanimate objects, so why would it be used here to talk about 私?

Thank you!

