Honestly I'm expecting a turn based mod to be out within 5 years of release, and that possibility excites me to no end.
While the possibilities and extent of modding is pretty much proportional to how much interest in a game there is, that's far less likely than even e.g. a mod for XCOM that modifies the game to go back to terrain-modelled chance-to-hit and time-units rather than the two-step board-game-esque movement/turns that the game actually has.
The point of me bringing up this specific example of XCOM is that it had its fair share of naysayers who just wanted an updated version of the original game with its mechanics intact, (sounds familiar) the fact that there's a modding community for XCOM, and that despite things like Long War existing, mods haven't come anywhere close to the experience of the original game*. Now extrapolate that from a goodness-knows-what system (FF7r) that might rely a lot on opportunity cost, frame advantage, etc for its balancing and try to put it all into a turn-based system or ATB system.
It's nice to have pie-in-the-sky 'oh modders will solve this' or 'maybe Squeenix will have turn-based DLC' discussion, but the crux of the matter is, there's a shit ton of caveats that aren't immediately obvious, all of which would need to be dealt with.
Every use case that works with a more action-y system that might not with straight-out old-school ATB (e.g. if you need to run to a certain spot in some encounters, etc) would need specific solutions/workarounds in a transition to turn-based. Everything from character growth and stats, materia system, equipment, and then by extension balance and game design, and by further extension re-thinking where you find certain materia or equipment would all need to be solved. In other words, you'd need to rip the game apart and rebuild a good fraction of it, which is a tall order for a development team that's going to be better off not worrying about it, and outright impossible for modders with simple hacks, injections and asset replacements.
*Firaxis have said that with XCOM 2, they're supporting mods to the extent that determined people could recreate time units-based gameplay if so they wanted, but that's already a whole different mindset and level of enthusiast support (PC-based game with all its precedents inherent to that status, acknowledging modding, etc)
edit: Yes, I'm aware that this exists lol