Is being a crossover fanfiction producer different from being a crossover fanfiction writer? Yes. But, it's still a viable way of creativity.

Hobby or not, my goals would be to still have very creative crossover fanfiction ideas and concepts using my own imagination, while having AI (e.g. Gemini, ChatGPT and Grok) write consistent in-character narratives and dialogues. From my end, what would be provided are original hard-effort plots and character contents (e.g. personalities and appearances). And the way it would work is if I use something like a 160-page composition book for writing partial plots, look up character contents and provide both of those things to AI. For every single plot-written page, I would ask AI to provide long narratives and dialogues. If there was to be a new crossover character anytime later in my crossover fanfiction, I would provide the contents of said new character, along with the current partial plot, to AI.

Human-produced/human-written crossover fanfictions, according to my personal history, would just have a lot of out-of-character narratives and dialogues, due to character personality contents being too complicated to fully understand. And AI-produced/AI-written crossover fanfictions definitely wouldn't work either, since it would have no human effort put into them, and that it would just write generic narratives and dialogues. Neither of which accomplishes both goals of mine. At the end of the day, human-produced/AI-written crossover fanfictions would be the most beneficial way for me to go.