i think it's a great idea because it gives you flexibility and it will bring in people who are afraid of your class. it also makes it sound to people like they are getting free personal training and they'll love that.
but i don't think you should commit yourself to a ratio of lifting to cardio -- having it be "group personal training" allows you to mix it up week to week and gear it towards what the people in the class want or what works.
This works great at our gym.
Fit Camp, not a very catchy name, but that's what it is!