Could this work !

Could this 2x4x7 tent be split into 2 levels and could it work effectively.

since you would be using leds its possible. you'd need a rigid framework 3.5 ' tall and something waterproof to attach to the top of it for a floor for your upper deck. i'd use 2 inch pvc pipe and fittings, and maybe 3/8 fiberboard with a double sheet of plastic in case you have any overflow. i'd recommend using a 4 inch inline fan if you're using it for odor control mainly, assuming the leds don't produce enough heat to require anything bigger than that. if you have 7 feet to work with, and you're using 4 inch ducting, allowing another 4 inches for you led array, and 8 inches for pots leaves you 26 inches. if you can come within 2 inches of the leds thats 24 inches for plants. i'm not familiar enough with cob leds to know if thats enough space between the plants and the lights. if it isn't, then you're scarpered.
you'd also have to do something about the ventilation. i've discovered from trial and error you cant use just a y fitting if you have a fan pulling through it, the main trunk will get 80% of the suction and the y will only get about 20%. you'd have to use some kind of reducer on the main trunk to get the y to have anything close to equal pressure. Actually, unless you intend to seal the two levels off from each other, i don't think you'd really need the lower exhaust hose, in that small an area, the upper one ought to be enough to extract any heat from the lower area, which would also net you 4 more inches of plant.
so remove the lower hose, close the top area air intake, force it to pull up from the bottom, and you get 28 inches per level for growth.