So... Let's say that you did get your favourite group of ENWorld people together...
... how long would the discussion/argument about what exactly to play last?
Only a reasonable amount of time, at least for me. Either a couple hours if we do it as an active, focused pre-game discussion (not quite "session zero," more like "prep for session zero"), or a week-ish if we do it as a passive "drop comments in the discord and we'll vote on it" or the like. I have strong opinions but I also respect others' preferences and strive for consensus and diplomacy. I would be opposed to playing 3e or 5e, but might be open to variants thereof (e.g. a gonzo PF1e game, a 5e game that would let me playtest the PrC I wrote, maybe even an A5E game if given some strong assurances that the system won't be misused in ways I have personally suffered under DMs misusing 5e), and I'm always up for a non-grimdark PbtA system, 4e, 13th Age, or a handful of other systems I've played and liked. Other than outright horrible offensive games (I mean games that are
openly racist or the like), the combination of homebrew/houserules, DM assurances, and group preferences can go quite a long way toward making a system compatible with my interests. Such things don't require a long conversation. E.g.:
DM: "Hey, I'm hoping to run 5e, what do you guys think?"
Enworlder A: "Sounds great to me!"
Enworlder 1: "sure, no prob"
Enworlder Prime: "I was thinking PF2e, but 5e is fine too."
Me: "Well, as you probably know I have my... issues...with 5e. Would we be allowed to use homebrew and supplements with approval?"
DM: "Sure, with approval. A5E stuff you can presume is pre-approved, but run it by me just to be sure. Did you have any homebrew you want me to look at?"
Me: "Yeah, I wrote a 'Silver Pyromancer' PrC that I've been hoping to test. I'll send you the link. Since this is a
playtest, if anything ends up too strong (or weak), I would want to work with you to fix it."
DM: "Hmm...seems alright as it is. What class?"
Me: "Sorcerer. I've written up the character mechanics, have a story that should be adaptable to most games."
DM: "Alright. Same goes for you all too, if you have some homebrew you want to use, lay it on me."
Enworlder A: "Nah, I'm good."
Enworlder 1: "ooh theres an alternate take on the circle of stars id like to check out"
Etc., etc.
It's not a
trivial task, but an hour or two of discussion should hammer out 99% of the issues and all of the deal breakers if they can be hammered out at all...and should reveal it if any can't.