ooh I've had another idea!!
What would BATMAN BEYOND be like in the nolan-verse???
Nevermind, I'll be quiet now
You don't need to be quiet. Here's my initial thoughts in terms of how Batman Beyond might look/work within the constraints of the Nolan-verse:
Since Terry McGinnis and the society in which he operates is very much more technologically-dependent than the Gotham City which Nolan introduced in Batman Begins, explaining his tech as Batman would be even more important, in terms of grounding the 'future Gotham' as much in reality as possible.
In terms of the Batman Beyond rogues gallery, I think you could very easily adapt the following villains to fit the more realistic constraints of Nolan's universe:
Derek Powers (pre-Blight)
Charlie "Big Time" Bigelow
The Royal Flush Gang
Ma, Howard, and Slims Mayhem