How the series should be referenced in ARR.

[Orophin]

I'll be upset if Cloud appears, but I won't be upset if someone references a "Spiky haired fella' with a huge sword"

Yep, exactly. If they want to bring old characters into the game, it should only be references in passing such as that.

[Delsus]

I agree, I don't want NPCs with the names of antagonists and protagonists from old FF games, some bosses are ok, like the elemental archfiends because they can fit in the lore, and aren't a huge part of the story of the old games.

Also bring in the recurring themes of the old games, Cid, boats, crystals, airships etc are already there, but slip a Biggs and Wedge in somewhere discreet (not a main character in the story) perhaps a vendor NPC, or in a new town, have them behind the guildleve counter (one of them local and one regional)

Also any I have forgotten, I would love a random Sandworm popping out of the ground anywhere in Thanalan (possible oneshot on lower levels for lulz)

[Ingolf]

They could take a great many lessons from FFIX.

That game was chock-full of Allusions to the previous FF's, but it felt like an individual FF with a strong story and its own flavour.

[axemtitanium]

FFIX was really good in that regard. "No cloud nor squall shall hinder us".