I don't think Tabata had the luxury of implementing his own concepts in the first place. The game's plot feels like an abridged, incomplete, T-rated, butchered version of what the Versus trilogy was intended to be.
You can pinpoint many of the ideas that's originated from Versus easily if you played the game. The kings of Lucis are the fal'cie, Noctis is a L'cie, the ring is something Nomura talked about 7 yeas ago, the Prompto being from Nifelheim thing was hinted on many years ago, with him using guns and all. Then you have the endless night (which is mentioned in Somnus's lyrics) and the "Noctis sleeps for 10 years" thing which fits directly with the sleeping motif that was very present in Versus, and not so much in XV.
I strongly believe the overall plot of the game didn't differs a lot from Versus in XV, it's just a very abridged, fucked up version of it.