Edward Elric from Fullmetal Alchemist would probably be very curious about the unique abilities in RWBY, like semblances. He might try to study them from an alchemical perspective. Ruby, on the other hand, would likely be in awe of Edward's alchemy skills and his mechanical arm and leg. She could see him as a kind of mentor in a way.
One interesting plot twist could be the alchemy of the Fullmetal Alchemist world interacting with the Dust in RWBY. For example, maybe an alchemist discovers a way to transmute Dust into something completely new and unexpected, which throws the balance of power in Remnant (RWBY's world) into chaos. Another could be a character from RWBY somehow getting involved in the Philosopher's Stone plot of Fullmetal Alchemist, leading to a race between different factions in both worlds to either obtain or destroy it.
Some characters might be quite shocked or amused if they could read fanfiction about their own story. For example, Edward Elric would probably be very indignant at some of the out - of - character portrayals of himself. He's a proud alchemist and seeing himself depicted in a way that doesn't match his self - image would surely make him fume.
Yes, it is. The manga has a perfect balance of action, drama, and philosophy. The themes explored are profound, and the character growth is very satisfying.
There probably are. Fanfiction writers often love to mash up different universes. In such a fanfic, Naruto could bring his chakra - based powers and blend them with the principles of alchemy from Fullmetal Alchemist. Maybe he'd use his Rasengan in a new way by incorporating alchemical transmutation circles. It would be a wild and creative concept.
Some characters might feel flattered. If the fanfiction portrays them in a heroic and positive light, especially if it emphasizes their good qualities like Edward's determination or Alphonse's kindness, they might secretly feel a bit of pride and be flattered by the author's view of them.