not sure if all of you plan on keeping your room 100% sealed, but if you dont... then keeping the co2 levels high beocmes a challenge.
reading into your cage idea... is this to support the plant in a vertical way, or to support horrizontal branches?
either way, my idea is this...
if you hang a vertical pipe from the ceiling, then you can use that as somethign to tie the plant to...
in addition... if this vertical pipe was pvc, and had holes drilled all over it, and capped at the bottom...
this pipe could be pumbed to the co2 tank you will be using... thus releasing the co2 directly into the plant, as well as supporting the plant, im sure you could use something to tie the main stem of the plant to the pvc pipe that would SLIP up the pipe easily as the plant grows, like a ripped shop rag, etc.
the only thing i havent fully figured out is how you would suspend the pipe from the ceiling...