Changes with Stella to Luna were already in place when Nomura was still in charge. Also, the initial story direction also changed under Nomura, based on the E3 trailer he directed, the entire party for the signing ceremony was removed by Nomura, not Tabata, you can tell simply by the fact that Stella (Luna) and Noctis were kids running through a field, something that didn't make sense at the time, as they were supposed to meet at the signing ceremony. Proof of both changes took place before Tabata took full control.
As much as I've argued how much this project is still based on the original project, I'm still (slightly) up in the air about that. There have obviously been some aesthetic changes, which really don't matter (that much) in the end, although I find it a little odd that Kingsglaive characters all look "euro" but in the game they still look Japanese, that is a bit jarring, but eh? whatever, I guess... Also, we can now intuit for certain that story changes to the game were solidified in 2013, maybe right when Nomura was removed, because SE said that's when Kingsglaive entered production.
Where I think we the fans are still confused about is Tabata stated in a translated intereview that a major lore element from Versus XIII, reaper worship, was "removed" from XV to assure ratings restrictions would be met. What does that really mean? Just de-emphisized or actually eliminated from the world? We still don't know because they wont show us anything meaningful about Insomnia. What is stranger still is there ARE reaper statues clearly depicted in the destroyed Insomnia artwork and the lore painting, and the Big Bang Amano artwork (at least we think, that last one has not been confirmed)!!
I wish they would just be more clear about this, but I think (hope against hope) that they are keeping the story under wraps, and this is why we can't answer this question. The irony is that I think answering this question would once and for all, show whether or not there are real fundamental differences. We know Lucis was supposed to be based on modern Japan (obviously it still is) but the cultural aspects of that society, ie that everyone worshiped death (Etro from FNC) is being held back. (I don't buy that "black is a special color to Lucians" line--WHY is it a special color!?) In Versus....Nocis's near death experience, ability to see "the light of expiring souls" ie. DEATH, was very significant to the world and where he came from. The main reason things still dont add up now, is because (almost) every piece of media or interview we have got since Tabata took over, have contained tiny story bits, but have almost entirely lacked lore inclusion for the world of Eos, especially as pertains to the Lucian people (outside the royal family itself). We had a hint of the coming danger
in the TGS 2014 trailer, but there has been no consistency or really sequence in story scenes as what we got under Nomura.
A final thought which I admit is conjecture, but without the explanation, I am left in speculation territory, which again is where frustration is stemming from: We were originally promised gameplay of events that were moved to Kingsglaive, so in the game maybe we wont really even see Insomnia at all untill it is destroyed, at which point the culture that flourished there before the games story began wil be rendered moot anyway. I think for people like our own Kagari, myself, and for many others, looking around in and exploring Insomnia-which was the first environment teased for so many years-likely is gone, and, the (seeming) ramifacations for the games plot that stem from that, are disappointing.
It is one thing to change character appearances (Regis), it is something else entirely, to drastically alter the lore which surrounds the main protagonist. Have they really done that? Would they really change not just some event, but a fundamental idea about a part of Eos AFTER Episode Duscae was made??? That seems insane, but then again they showed the OG old Regis all the way until Gamescom 2015! I am almost convinced that this is still partially an elaborate SE troll, like how they kept the Regallia being the airship a secret. While I appreciated that reveal, this is one where I wish SE would shine some *Lucis* on the situation
