Here are some answers and images in regards to your questions.
There is room for 4s batteries. The depth of the battery compartment is 5cm. This should fit most 4s batteries but probably not all of them. An included foam inserted comes with the vehicle to take up the space when using a 2s or 3s.
We realize the Mirage is not for everyone as there are 16 screws that need to be removed to take off the roll cage. I have attached an image with the process to remove the roll cage in its entirety. I have been running a prototype for months and though it only takes a few minutes to remove the entire cage, I decided to just run it without the seats and drivers which makes it easier to work on if needed.
Here is an image of the Mirage with the cage and body removed.
(Last edited by RedcatRacing : 2.28.13 at 4:33 pm)