i don't see how you are going to be able to get around inside that room with the door at the end like that. i mean that is gonna be really tight. why not do a door in the middle of the 7' long wall. then you can walk in and have a 400w light on the right and one on the left. you could easily do 4 smaller plants in 3 gallon pots on either side. then you'll have some room in the middle for equipment as well. you might end up needing a dehumidifier or something. then, since you have 2 sides you could do a 30 day perpertual. harvest one side every 30 days. that would be nice.
where are you going to veg the plants? the tent idea is perfect for the dark period. i do the same thing. i have a tent that has a/c and a dehumidifier with some green lights and regular lighting. it's where i do my dark period, trimming and drying. i also cure my weed in there. too humid where i live.