My understanding is that all are actually parts of one human personality. Like all the parts together represent all aspects of one human personality. Alters are not a "full human personality" even if they can deal with a wide range of things.
So in my understanding of it, no that part would not need to become more than it is for you to heal it. That part deals with one particular thing so to heal it you learn about that one thing that the part is needed for.