First off, it would just be called The Return to Frankburt's. All previous Freddy's content would've been mostly absent, focusing on a purely original cast based on preexisting characters. It would've probably pulled Sugar from Winter Wonderland and Frankburt from that game, with more distinct designs for the characters. Buster Vigo and Dug would've been there since the first game in my ideal TRTF.

My timeline would've been TRTF2 > TRTF1 > TRTF3 > TRTF4 > Frankburt's > TRTF5 > RADSLA

Frankburt's is so high up in the timeline because I imagine it is set in the future, where the company owning Frankburt's would try to reboot the restaurant, only to fail. After all, no one wants to bring their kids back to the same company that brought a corpse animatronic into a previous establishment. TRTF5 would still be a factory, although in an abandoned state at the point in time, and would have mostly produced Frankburt's animatronics, with some in mint condition and others not so much, and some would be hybrids inspired by that scrapped concept. And one suit made by Gron back in the late 80's to Early 90's being the first springlock suit to be made as a prototype. Employees would call it the Torture Device (vaguely looking like Frankburt before his design is finalized) because of how unstable it is.

I do know that I would completely rewrite Gron, might even rename him, since his name is literally a translation of Green. I want him to be a more serious threat than some guy who slips on soap or gets his head springlocked/tortured. I'd imagine him kinda being like the main guy from The Shining, possibly? Gron would mirror Springtrap by becoming Lockjaw when wearing the Torture device. It would make more sense to have him be a pre-frankburt design wise. Being the first in universe springlock, being so dangerous It would kill in an instant if worn by an idiot.

Also, he would be really malnourished, as he doesn't focus at all on his physical health.

Radsla would be an experimental location trying to bring Frankburt's back from the dead for the last time, with some old models returning and some new. With Locations being all over the world. It would have the most endings, 3 in total, leaving it ambiguous as to what happens to the company. Super Cancer won't be a part of the story either ( Like, seriously, what the fuck is Super Cancer )

Alison wouldn't be canon or unimportant in-universe probably with the personality that of the current US president. As I don't like his character and I can't be bothered to think him through.

Vincent is a part of the FNAF CAST despite having a different name from William Afton, so he would be removed entirely from the story.

If I had more time, I would polish this up, but I've been mainly trying to avoid making any more Fangames of Fangames. TRTFWW and Halloween Horrors were enough for me personally, LOL

Anyone is free to use this as a base concept for your Fangame, as I don't plan to do much with this. Just credit me or something.