I'd personally rather they kept this series as grounded as possible, and let whatever the hell is going on over in the DCEU handle the weirder stuff.
No interest in Robin. Don't see this Batman putting a child in danger. Dick Grayson as a ward is fine, but no more.
There are some of the rogues gallery I'd rather they stayed away from, like Clayface, Man Bat and Ivy. But would love to see takes on characters like Mat Hatter, Hugo Strange, Court Of Owls, Scarecrow etc. They'd all fit in with Reeves's sensibilities for this project.
I firmly believe Batman is always at his most successful on screen when he is kept as grounded as possible. And kept in solo projects, away from the more fantastical stuff, and characters.
That's why I've been so pleased with what Reeves is doing so far. He's making a grounded, mature version of Batman that embraces as much of the lore as is possible within that framework. I see no reason why that should ever change.