Well, I think as a level design it is probably Interesting(nose tap). I'm not sure if it would be fun to play on though, but would at least be an interesting arena to create and play around in. Sadly, the DG engine very likely can't support this:
Dynamic Grunt paths sounds like a real pain.
Dynamic pathing in general is going to be a trick.
Inevitable bugs like Erebus batswarming to a location on a gear... which doesn't exist after he arrive.
Other than that though, I applaud the thought you put into the piece. I would suspect you'd make a good level Designer if you had 3D skillz.
Dynamic pathing isn't too hard. There are lots of algorithms that can quickly determine the shortest path to your destination like A* and Best First. The path calculation could be refreshed every second or so , so that the minions don't fall off the map or something by trying to take a path that was good a second ago, but has since changed. Also, not every creep has to find a path for himself. Only one creep per wave needs to calculate the path, and the others can follow him.
And bugs like that erebus thing can be fixed. All bugs should be fixabile. Like if erebus accidentally teleports off the map, he is teleported to the nearest surface he can stand on, which is not hard to program.
The real problem is the game engine which I am not sure will be able to handle this map without some core modifications. And I'm not sure GPG will be to thrilled about core modifications...
But anyways, great map ideea .