I'm pretty sure stunts and twists were discussed at length... perhaps even tried waaaaaaaaaaaay back when... but the word was it was buggy as hell and therefore NGTH.
As for slants and stuff, I'm gonna bet that the way the game is made... the way the dot AI works and how players react to vision checks... this wouldn't work either. As soon as a dot 'sees' something, whatever he was doing goes away and a new 'plan of action' is charted. Most D-linemen, in a slant style, would abandon it before they for 2 steps off the LOS and return to 'read and react' which they're built for.
Lastly, even if it WAS put in for the Defense, the Offense would immediately scream 'foul' and demand their own O-line adjustments and, before long, we'd have a right fine mess.
So, unlikely it will happen but I get where you're coming from. I've seen MANY a playbook from MANY a football game or team... real or imagined... and plenty of them have stuff we'll never see here.