I should also note that in the floorplan (it's old), the "living room" is now a gym, and the "dining room" as pictured above is more or less just an entry room off the garage.
I'm not totally familiar with these systems... but, I don't think I'd want the unit drawing fresh air out of the garage.. Gas fumes, exhaust, lawn mower clippings etc do have odors. PLUS... in todays construction that wall has to be sealed and fireproof.
The compressor/condenser would be outside of the garage under the deck. The refrigerant drain, and electrical lines run through the wall and out to the compressor.
For your question.. I'd go two.. split the zones because those things never are as good as the manufacturer says they are. Personally.. as an HVAC technician.. I despise these machines for home use for several reasons.. but I understand their retrofit uses. If you're mechanically inclined at all MGH.. they are EXTREMELY easy to install yourself.. just have a licensed AC dude finish the compressor side of things. You can even run the copper.. they typically are just compression fittings.. no high heat brazing needed.
I remember asking you about these a year or so ago, and you mentioned the lack of dehumidification and allergen control. These do have anti-allergen filters and a dehumidification mode. Whether they are at all affective, that has yet to be seen or proven, but I'm really at the end of my options here. My house layout is just so broken up, that ductwork would be ridiculously expensive and obtrusive. As for installing them, I've heard it's pretty straight forward, the only concern of mine is the warranty is void if you don't have a licensed tech install them.
