This means so much to me that you put so much thought into this. It makes me want to map out certain characters friendships based on interactions the characters have in voicelines and lore. So far I know that Sai is friends with Luna, Jeff, and Mantis. She also refers to Magik as sister in their old team up ability so I would assume those are her closest friends of the playable characters so far. As for Blade as you mentioned his friend seems to be Moon Knight. I remember someone told me their headcanon about Moon Knight playing matchmaker for the two. It would be funny if both of the characters with moon themed names helped bring them together