I would add transoms above the garage door(s) or window panels in the garage doors for natural light when the door is closed. I prefer the transoms as they're high enough to keep from getting hit with toys etc, and keeps the gawkers from looking in, if that's an issue. As for radiant floor heat, it's a bitch to mount things to the floor (like anchoring a platform lift) if you don't know where those tubes are in the floor. Plan for anchor points, run the tubing in the floor even if you can't use it right away, you can always plumb into it later. Oh yeah, I'd go standing seam metal roof too, you won't be replacing it in your lifetime. Sounds like you're having fun, good luck.