A possibility for the live plants:
Keep them in plastic litter pans, like you can get from Walmart etc. With a jigsaw you could cut a hole to size in the floor of the cage and set the pans with plants in them. Granted, you'd have to give up 4-6" of height b/c you'd actually need 2 floors; one that the actual cage would sit on and another 4-6" higher for the bottom of the pans to disappear into. This however would probably also facilitate a flush level "pond" with a drain. Then you could just alternate pans of plants if some get damaged and/or pooped on/in.
For an idea of what I'm talking about, check out the pics in my photo album of my watersnake's enclosure. It's a regular 20L glass tank, but I made a little platform that I inserted into the 20L such that a 12x8 litter pan (water dish) sits flush with the rest of the floor.
I'm not sure how well this would work for a big, strong snake, they might be able to get it pryed up and get under it, but you could always get proportionally larger pans to make this more difficult...
[addsig]
