I quite like multiple dispatch. It's odd to claim it's not OOP, since a relatively old object-oriented system, the Common Lisp Object System (CLOS) uses this as it's fundamental construct.
A long time ago, I wrote about and created an example library for multimethods. Lots of other folks have done so as well. Mine was old enough to precede decorators, which I think is the best way to express it in modern Python. Guido had demonstrated a simple system when decorators were pretty new.
While I would like an implementation added to `functools`, I think it's exceptionally unlikely it would have anything to do with speeding up Python. It's a nice way to express certain programs, but not any slower or faster than other styles.