Another arkhamverse game could have worked if we focused either on a Batman Beyond entry (do you think its a coincidence that B.B's suit is among one of the most popular in the series?). Have Terry finding Bruce in hiding, already too old to keep the fight and all leads to Terry continuing the legacy and most supporting characters not having much faith in him. That is until the game's climax happens (maybe Blight or something) and Terry stops him, earning everyone's respect as maybe we leave on a sequel tease with Inque or something.
WB Montreal, the Origins’ developer, had leaks about them creating something similar to this. They were going to make a single player Damian Wayne title that would function as a mid-section between Batman and Beyond allowing for villains from both to appear. Too bad WB got caught up in live services, thinking they need to compete with Avengers, and ultimately making a crappy game that they needed to change last minute due to the failure of their supposed competitor.
There is also the route of a Superman game like people have been requesting and even Rocksteady is implied to have shown interest in doing so before it being shot down by Warner (which probably led to them greenlighting this mess of a game instead). You could say it would be boring but a Superman game where you play as a Year One Clark thats still getting the hang of his powers or maybe a prime Superman but the plot has him either weakened or facing some real OP Mfs like from Apokalipse.
Arkham Knight released in 2015. Assuming Superman was already in production, this game would have started development around the time of the first SS movie, which did well due to Harley merch selling. Superman was scrapped as they pitched a depowered Superman to Warner, with Warner being very disinterested in the pitch and pivoting to SS as the company is very adamant about it being their Guardians of The Galaxy for some reason. Should also be noted that WB stated back in 2010 that SS would get a game, so development has been an over-decade long disaster for this stupid project. Astro-turf Squad is such a shit IP outside of comics. I have no idea what Warner sees in this consistent failure as Teen Titans honestly makes for a better Gaurdians substitute, and is shocking in how this successful IP is not used more beyond animation and a low-budget streaming series.
Teen Titans would have been a good continuation if they wanted to go the multiplayer route with a lighter tone. Have Knightwing form the group in Batman’s absence and have a multiplayer squad of Starfire, Cyborg, Raven and hopefully Beast Boy (might have animation trouble). Hell, they already had DeathStroke, might just build off the previous and have him take on Knightwing as a revenge against the Bat. It would at least give him a chance at some boss battle redemption after Knight’s pitiful tank battle.
The weird part is, they are making a WW game. We just haven’t heard anything about it since Game Awards 2020 I believe.