Everyone is rightfully miffed that Final Fantasy VII content (let alone general Final Fantasy content) is so sparse, but I still like what they did with what they had.
In World of Light, in the Sacred Land, the Zelda area, the one who guards the Master Sword is Cloud. He's the one who gets the honor, and, better yet, it's mandatory to unlock Young Link before fighting him, allowing you to reenact those OoT vs. FF7 wars of the late 90s.
There are no Final Fantasy VII spirits beyond Cloud's Smash renders, but Cloud DOES appear in a Challenge Board photo, spoofing Aeris' death, that's funny / sad.
Also, if you're unlocking characters solely through the multiplayer, Cloud is the very last third-party character you unlock, to cap off on the whole "it's crazy that he's really here with everyone else, isn't it?" sentiment around his inclusion.