Do you think you could look into unlocking dota_all_vision ?
That wouldn't actually give you a maphack. The units which would be obscured by the fog of war would appear to be standing still doing nothing until they reappear in your vision. The information of unit location isn't actually sent unless it is within your vision.
One more thing which could solve the problem of the cut off. If you enable camortho to be changed and turn it on, then change the c_orthowidth and c_orthoheight settings to match your resolution (width being your screen resolution multiplied by some constant, height being your screen resolution minus 197, then multiplied by the same constant) you can set the camera to any distance, provided you also enabled fogui and turned off the fog effects (otherwise everything looks light blue and you can't see shit). In order to set camortho to 1 in a replay of a demo, you also need to set sv_cheats to 1, this can be done in a demo.
This will also make the angle steeper, though not quite a direct over head look. If you don't like that, you can use the scroll wheel to tilt the camera a bit. An interesting thing about this is that the setting dota_camera_distance will change how much it is tilted instead of the actual distance. the c_orthowidth & height commands set a static height for the camera.
Here's a screenshot:http://i.imgur.com/tvin1.jpg
I have c_orthowidth set to 4 times my screen resolution and the height as my resolution - 197 * 4.
Using the scrollwheel to tilt in this mode will actually produce some clipping at the bottom of the screen, making it almost look like a board game. http://i.imgur.com/zHNdQ.jpg
Another thing about this is that you may need to set the camera speed higher, it moves very slowly without doing so. Moving the camera with the middle mouse button moves it even more slowly than using the edge or arrow keys.
When I fist messed around with the camortho command, I thought it was useless because all I could see was fog. It could be a great way to set the camera height if the fog commands are unlocked.
As you may have noticed, the screenshots are very dim / low contrast. Some additional settings may need to be changed to fix that. Maybe one of the cl_globallight things?