Very Nice Space! Looks like some sort of 1st floor basement?
Regarding the smell, I would maybe air seal the ceiling first by installing a layer of drywall on those joists & maybe even insulation or foam. A bead of caulking around all air gaps. The more sealed you can get it the better. Although not really needed, just a suggestion. You could also build smaller rooms within the space, or set up a couple of grow tents, so many options.
How many watts are you thinking ? Or how many plants do you picture yourself growing at once?