Sounds really cool. I'm finally going to get started on my new cages next week (assuming I can get the plywood by then). It should be a fun project. I just have to get the plywood first to start, and my dad's friend (who is an excellent woodworker) is going to help me. They are going to be stacking cages, and three of them (though I only have a bearded dragon and a mali right now...the third is going to serve as storage space until I move out). They are each going to be 4'x2'x2'. My beardie will be on top because he has the lighter of the two setups (since I don't usually use sand or dirt in his setup, and when I do it's limited to certain areas...for now i use shelfliner and once he's done with parasites I'm going to try slate tiles)... my mali is going to be in the middle one, so I think it might be a good idea to put extra bracing in the ceiling of the bottom one to hold the extra weight from her digging box and rocks. That's something that we can add in at the end though, so I'm not worried about it.
I really like the idea behind your setup though and I can't wait to see pictures of it. I think for my mali's new cage I'm basically going to have a bunch of nice hides, a basking platform that will either have some slate on it or cork bark, and some grapevine for her to mess around on. I've been debating what to do for her fake burrow, but I think I'm going to take a flatish rubbermaid container, maybe camoflage it with corkbark and stuff, and just fill that with dirt. That way it will be easy to water and everything. The rest of the tank is going to be very shallow, but it will probably be an assortment of dirt mix, some sand in spots, and some slate tiles broken up. I'll post pics when I get done with it. I want to make the cages for functional for the lizards, but I also want it to look nice and natural. I think I'll put some small plants in too.
Good luck with your new setup. I'm excited about mine, because I think it will be a fun project.