Upper Levels Need ideas for constructing Patio!

I have wanted to build my piggies a patio in their cage for quite some time, but every time I plan to go and do it, I get stuck on some kind of detail and it just hasn't happened yet. Your ideas and help would be greatly appreciated!

Ok now on to the details

My cage is a 2X4 C&C with a lid (due to my cats). The way I constructed the cage is by using the front of the cage as the door, so instead of the lid being able to open, it is solid, and the front wall opens down. The reason I did this was because at first I started with carefresh litter and found that if I had the front open I could pull the whole coroplast bin out and it was easier to clean that way. Since then I have switched to fleece (what a money saver!!) and I'm wondering if I should modify the cage to open on the top rather than the front.

I really like the way @Traysea used the wonder bars to support her patio and it also allows me to fold the patio up and out of the way when it's time to clean the cage. But with the way my cage is constructed with the door on the front, I wouldn't be able to use them. So I guess my question is, should I go ahead and modify the cage to put the lid on top and save myself a whole lot of trouble? Or should I keep the cage the way it is and find a creative way to support the patio that i would like to install?