However, wait till you get this: If you had such a meta-RPG system, not only could you put that on top of any RPG that you like, you could also stack as many levels of meta-RPG system on top of each other!
"My character has a secret crush on your character's character, so, to impress them, my character's character makes their character cast an extremely complicated spell, citing every single rule involved while looking your character's character straight in the eye."
"My character notices your attempt, but since they find your character absolutely disgusting and I just failed an acting-in-character check, their character is very unimpressed, also fails their acting-in-character check and looks at their notes while telling the DM that their character wants to shoot an arrow into your character's character's character's foot. Anyways, what are you doing after this? Maybe we could get drinks or something?"