I'm gonna be honest, I'd love to see a PS2-style GTA Clone with an old-school horror theme and Halloween motifs. Yeah, Level 7 of The Simpsons Hit & Run had that but I'm talking one where you're not bound by a T rating and the monsters are actually dangerous.
Heck, a low-budget M-rated GTA Clone that followed the same story structure as Hit & Run would be a very unique idea. Maybe have seven chapters and each chapter is a different point in the timeline?
I probably wouldn't have multiple protagonists for each chapter but the idea of each chapter getting a little darker and weirder as the story goes along before going full-on horror in the final act would be interesting.
The problem is that a lot of "ideas guys" have these lofty goals and their lack of understanding and skill makes their plans grandiose and unrealistic which is why everyone hates them. I'll admit, I have no skills as a coder, programmer, or developer but I know that you'd have to keep any independent production small in scale to save on money and technical limitations.
Open world games pose a particular challenge since even indie developers with experience will get lofty and end up overpromising while the actual in-game map is too empty and generic.
Morrowind and Vice City (GTA 3 to a lesser extent, but it's sparse by today's standards) had the solution of a relatively small in-game map that made up for the width with depth. There was more to do and you could soak in the atmosphere.
If I were to type up a design document for an old-school GTA Clone, I'd keep that in mind. A small map with only a few areas but the areas have a distinct look and feel while the story and gameplay would be engaging
Never heard of a potential Goodfellas games but I do remember there was a canceled Taxi Driver game.
I remember that one too, I think it's possible that the Goodfellas license was picked up alongside Taxi Driver and that's why we never saw anything come from a Goodfellas game but the canceled Taxi Driver game is more well-documented.