GnomeBob
So I am not really a super fan of game novels, still your game got me thinking of legendary mechanic/reincarnation of the strongest sword god, and I got this idea(about a hero association tie in, and you can add the path system), basically every 60 levels is a tier, and tiers can be classified into 5 levels(Wolf ×1, Tiger ×2, Demon ×5, Dragon ×10, and God ×20 and up), so using the path system every npc and gamer is classified into the five threat levels, so every 60 levels the players have a tier mission and depending on their path level they can have their threat level reevaluated, so you could limit the player path depending on their threat level, a wolf can use only one path level per tier so they are really weak even a level 300 wolf would have a path level of only five, meanwhile a dragon at level 300 would have a path level of 50(basically Harry), that would give the players a realistic view on strength since it may vary widely depending on path level, it could also limit the players you could make the first 60 levels a open mission to gain a higher threat level, and depending on their threat level you can limit their tier level, so a wolf can only ever be tier one, a Tiger tiers 2 to 4, Demon 5 to 9 and so forth.
Multiple reincarnators have been done multiple times, but you probably knew that. My favorite one is the Instant Death light novel series, and if you haven't read it, I think it matches quite well with what you're going for. It's an original fiction so no copyright things from other worlds but it features a vast array of OP plz nerf power types. I think you're limiting yourself with the number of universes in your future story. Maybe keep it vague and add more power sources as you go along and do more research while writing the story to never run out of ideas. There's no reason for the super system to let players know ALL the systems available. And any system can get updates hint hint.
Bla Just bla with all this game stuff and Dr Who and wreck the zombies for reasons… theres plenty solid material Like Gwenom or the king in black, planet hulk, the Fear event, more MCU stuff lIke Dr. strange’s arrival and Ultron, really loved what they did with Zemo lol. but it feels like you’re rushing to sunset this story to move on to your next project.
If your looking for other universe quests the “Harry Dresden” book universe could be a cool tie in or you could do another trip through time in space. A long time ago in galaxy far far a away “Star wars”. Plus for the Star Wars it could be funny if MC runs into E.T. Since his race is part of the Senate in star wars as an Easter egg