I think you'd have to totally redo the MP with the code mixed in. Currently, there doesn't seem to be any AI encoded in the MP game. The manhacks SORT of move around a little, but mostly just their general up/down floating and bouncing off things. On the upside, you can grav gun them and run around using them as buzzsaws.
Maybe the MP maps have no AI hint nodes? And possibly the other sorts of AI present in the singleplayer game are also enabled in Hammer somehow... I dunno.