well freash air is pretty important i would build some grow boxes in thier that look like storage cabs. also in the front where you open the garage door have some stuff there so it looks like you are going in to work on a project. whille you may have a legal grow at some point still dont want to get your plants stole.
back to the freash air. i would try to get some sort of home made co2 kit so higher temps and lack of fresh air wont be as dramatic.
and do keep the air in the room moving