I agree with Heike that the needs of the 3 activities you mention are somewhat different. That does not mean that they cannot coexist, just that you will need a really clear plan vis a vis schedule, as well as set up to make it work smoothly.
One example is temperature. My preferred temperature for yoga is 74 degrees. If you plan to offer any form of ‘hot’ yoga it will need to be higher. If your room is colder some yoga enthusiasts will be turned off. If you are sharing the room with group ex and the classes are back to back the yoga temp. will be way too hot for the cardio classes.
There was a question a while back as to what you would have in your studio assuming you could have whatever you wanted. (http://www.ideafit.com/answers/what-would-the-ultimate-fitness-facility-… ) I did not reread my answer, but I do remember spending some time on it, so it might be helpful to you.