I've read, while I was researching for the memories, that having all 13 memories adds a scene to the ending.
That means to me that the ending can be variable depending on what you did/skipped.
What elements of the ending can change, and the change depends on what?
PS: This is kind of a question of "What are the different endings, and how to I reach them?", but it doesn't seem that there are massive changes to the ending depending on what is done (A main character wont die, or turn on you, etc.). So thats why I'm asking more on a modular kind of way.
Damn I think I'm confusing. Am I clear on what am I asking?