Not even the OLD code will allow that. Too many 240v appliances have 120v features inside (like lights and fans). You are using an isolated ground for common which is not allowed. Using common for ground IS allowed (old code). Doesn't matter how it's labeled, as someone down the line may plug something else in that's wired different.
Using common for ground is just as safe as using isolated ground for ground IMO. Maybe safer because the connection is better. Drop a ground rod into dry sand and you've got dick for a connection.
Now I'm not an electrician, and I'm going from memory on a class I took in the late 80s, so I could be wrong.