Deepforest, loss of identity (ego) is something that is recognised in psychology.

In particular, when trauma occurs, the way in which a person thinks of themselves and the world around them (their ego) disintegrates very very rapidly.

So no, letting go of ego is not the road for the person without any sense of identity. Nor is the illusion of higher/lower selves helpful to someone with narcissistic personality disorder.

There are so many different clusters of symptoms that are called mental disorders, that no one way can fit them all.