I haven't thought this all the way through, but at first glance this is idiotic. If I were a CEO and my company was taxed this way, the first thing I'd do is lay off every employee and hire only contractors to work for me.
How would that help?
I am not advocating taxing corporations on their gross sales, but why would it make any difference whether it was your employees or some contractors who were making the sales?
If contractor’s can do your work cheaper, you should be doing it in the first place. ALl that proves you are not a good manager and your contractors are. It is better that your employees be working at the contractor than your in-efficient business.