Many Blood and STP keepers use racks with the Iris "christmas tree" tubs. I *think* AP makes them and I'm sure C-serpents could make a rack with them also. You can get the christmas tree tubs at walmart, homedepot, etc. during the Christmas season... They are also basically a 40gl breeder footprint or larger and will work well. I know people that have housed dwarf boa males in these for life, as they are ~18" tall (at least).
For a carpet, a custom pvc cages is def. the way to go. I keep my jag. in a 4x2x18" AP pvc cage with shelf and climbing branches and he uses every inch of it...always out and on display and moving around.
If you are considering stand-alone tubs for any snakes, make sure you use luggage straps, binder clips, or other means to secure the tops, as the "tabs" they come with aren't enough. I prefer large binder clips.