well, I want to move to your neighborhood. in Palm Coast to get 4 acres it would be 16 lots, and at around $40,000 per lot... well, you get the idea.
the garage looks great. I would suggest individual dedicated exhaust fans.
it may still not be too late to do a vaulted truss to get that lil extra space if you should ever wind up with a lift.
is the front 18 by 18 for parking or porch? I have seen a few shops / barns and a raisd front porch seemed to add a bunch of character....
the other thing I have seen, in a great garage in Hastings florida (owned by the local bank president) was a glass wall separating the clean room from what I would call a entertaing / living room.
I suggest that perhaps a sliding glass door could be put in the clean room wall. you would have to protect it during certain operations, but it is just a thought.