Hey Michael,
Believe it or not, I have done alot of thinking on this. We will be too far out for natural gas, but I am thinking of getting a propane tank for the house and garage. I have looked into some cost effective radiator style heaters that run off of gas, and it looks to be somewhat efficient. Its better than electric heat, but I am concerned with propane. It's not regulated, like electricity and natural gas.
A/C is another sticky point. I live in Southwest Idaho, also known as The Desert. Our winters can dip down to the single digits, but our summers hit triple digits for 5 to 6 weeks at a stretch. Which ever way I go for A/C, I am going to include a ceiling fan.
If the trainroom gets to be sunken, which is my hope beyond hopes, I wont have to worry about the massive degree shift, as most basement/sunken spaces tend to be more mild. That is one reason our friend put his shop under his garage. He is nutty about wood working and didn't want to have his stuff be effected by climate change as he works on it.
George