Vented Attic Grow - closed or open?

I have to grow in private. My first plan was to grow in a closed closet (see post). But I went exploring in my own home and found this place:

It was revealed by unscrewing a boarded up area in a very small AC closet I find hard to get into. It has two vents inside, the silver one goes to a wall vent in a room that is rarely occupied.

The room has an angled ceiling, at its max, is about 4.5ft, but angles down to maybe 3. My usable floor space is about 4ft x 2.5ft. (havent bought seeds yet, advice???)
I was planning on using this vent as my source of ventilation. I have two different ideas on how do this. Plan 1 is box in my plants and lights, and have an carbon filter on a exhaust fan to that room. Plan 2 is to just plant in the open, with lights in the open, leaving the vents just kinda there, but still not making the mistake of leaving them unfiltered.

First picture shows the current setup. Although the vent is not always on (it controlled by the AC and temperature), the fan would be pulling air that is 'available'. The walls are either actual walls, or insulation.

Should I even bother with a box, or some sort of concealment, like a box? Or will the odor escape eventually? Any past experiences/posts?

I can't wait to post my progress on the forum.

Bump. Anyone?...

I'd say plan 1.

As long as you exhaust through a carbon filter smell will be fine. Gonna be hot in there in the summer would be my concern. What system and lighting are you planning on? 4.5 is pretty short.

Your going to want an inline fan constantly expelling air out the exhaust to create negative pressure so smell doesn't leak out.

Plan 2 would allow for a lot more space and since it is insulated I would not have to worry about my AC $$$, I think that's what I'm going to do. Temperature shouldn't be an issue, with the AC and the weather it's average about 76 upstairs.

Johny, I'm not too sure about lighting. I have a few new fluorescents laying around that should be able to pump out a few thousand lumens, probably just hook those up.

I guess I'll go and order my seeds, any links of what would work best with only 4.5 ft? Cloning or seeds?

edit: blimey good point, gonna score some PC fans or one of these.