I like this idea, except for the heroes part
If you could put heroes in without the creeps, while still keeping it balanced so that they arent super powerful like the heroes in wc3 it could work
Maybe re-balance some of the units to and bring back the stuff blizz showed years ago but didnt get into the final game
And definitely put the lurker in
Also, instead of a text command for the tutorial, you can use a databank to tell if its their first time playing the map, and if it is their first time then show them the tutorial