Everyone plays Final Fantasy games for different reason. Some for sheer nostalgia of the franchise. Some just to battle. We know for a fact some people play FFXIV just for the gameplay--people spam left click to skip all story, which they couldn't care less about, to get to more battles and to level faster, etc.
For the people who like the series just for nostalgia, I understand how crossovers are cool content.
However, I play Final Fantasy because I want to be edified by a great story. This demands a great plot and great characters. My entire concern in this thread is to that end alone. When I hear Yoshi say that he's going to make series crossovers "a natural part of Eorzea's history," I feel that this is a damaging move to the story and plot--the whole reason I play the game, and I tried to make an argument for why I think that is the case.
For someone who cares most about story, I have to disagree with you. Lightning or Cloud showing up in FFXIV, and being a natural part of Eorzea's story and lore, is a bigger deal than making snowmen or reindeer suits. It may be the same old same old seasonal event from the perspective of someone who plays for nostalgia or for battle, or who is just an item collector--but for someone who plays for the story, it matters.
I don't want to come across like I'm throwing a tantrum if I don't get my way. I'm really concerned about this, and I wanted to express my opinion in a reasonable manner. I will still play FFXIV if these crossovers go forward, if I can ignore them enough or like the game enough to turn a blind eye to the crossovers. But if this game does become a fanservice-fest, it really is something I would quit the game over. You say it's "something so trivial," but a strong, integral story is not trivial to me.
You say that we won't be forced to participate in it. That's your own assumption--but even if you're right, Yoshi has already said that he's making these crossovers part of the lore. Thus, for people who care about lore, you're forced to participate. That's my whole point.