Double grow rooms with a common scrubing plenum room

OK, I hope this doesn't get too complicated, and I actually feel ashamed to ask because I used to work in the power generation industry, and moving air was a big part of what we did, BUT I'm plum stymied. I am using a sort of 1/2 upstairs to bust a quick double crop and get the hell on with my life in a new town (on the beach, baby), near my favorite place in the world, New Orleans (where I'm going, NOT where I'm at now).
I live very close to some very fine, very inquisitive Christian neighbors, and odor control is not just imperative, but IMPERATIVE. I plan on using both of the rooms at the same time to quickly show an auto flower movie, while simultaneously starting the germ and veg cycles of some higher yielders (maybe a few WW and Blueberry for me, and I am still undecided about the main feature – suggestions would be nice – I’ll share if I see you on Bourbon Street – I’ll be the guy with the ukulele playing zydeco).
I’m going to use the center closet as a common scrubbing plenum for both rooms. I am actually hoping for MASSIVE overkill on this. I am using a large ozone generator and an air purifier (just because I have one) in the closet to pretreat the air. I am also building a large carbon scrubber with a blower. At the exhaust, I’m using Ona gel (laundry scent) in a small inline cage, before venting to the outside through a 4” pipe.
Question 1 – The scrubber – I’m using screen printing screens with loose carbon pellets (around 5 screens) in an enclosure with a blower pulling from the bottom, and out to vent. – This should work, Right?
Question 2 – Heat – I am using 2000W in room 1 and 600W in room 2. All of the lights are inline, BUT, it’s fixing to get cold where I’m at (a big reason to move south), and the attic is mostly uninsulated. If I just pumped (or passively allowed) cool air into the main chamber, do you think I could avoid running separated ducts for the lights. I am trying to keep the air flow as simple as possible so as not to short circuit my plenum. What if I literally just pointed an air-conditioning ducts across the tops (like a cool mountain breeze)
Question 3 - I have never worked with autos before. Is it unrealistic to think I could get 30 plants in these areas (tight Scrog), and say in 5 weeks start the phase 2 plants (everything is from seed – if I have time I’ll take a few good clones, but I’m just spending the money on fems cus I need to move fast – about 8-10 months), and sort of find spots for the rest for the next few weeks until the autos are ready.
MAIN QUESTION – I am missing something about this plenum setup, but I cannot figure out what it is. The rooms themselves will be sealed, resealed, wrapped in plastic, resealed, and heat-sealed (seriously). Ain’t nothing get in der boys and girls ‘cepten what I want (practicing my NOLA accent). Is my math all screwed up in being able to use a 4” vent on this, because I can vent other places if I need.

OK here are the plans. I just feel like I’m missing something.

Assuming the outside air is available, it can cool as efficiently as an AC unit. But a couple of things come to mind.

A. You will need to introduce fresh outside air fast enough to balance the heat from the lights etc. IIRC correctly, 3500W = 10000BTU. So you will need cool air about equivalent to a window unit running on high.

B. It's not clear to me how you are exhausting room air. Perhaps I missed it.

C. Silkscreen is fine mesh and will impede flow through the filter. I assume you want it for particulates? Either the screen has to be large enough or the blower has to be strong enough to get the cfm you need.

I am running a 200cfm 4" inline vortex. It does a good job of extracting the heat from a 600W lamp and a 5000BTU AC unit. But I have no filter on the intake.

I say if a component is crucial, over build. Plenty of excees capacity means you have room for contingencies and your equipment is running in its comfort zone. A 6" duct fan is not that much more expensive.