Lots of good thoughts and suggestions. While I know what I like to build (furniture, cabinets, thingys, you name it), I didn't stop to think much that everyone has their comfort zone and it is different for all.
Like you Jim, a number of years ago I had a 40 x 40 garage that gave my wife room to park her car and the rest for my shop. Then we bought a cabinet shop and had 15,000 sq ft. Today I have one stall of a three car garage. We are going to be moving again soon and I may have the chance to build.
For my perspective, I think a 24 x 36 +/- is about the right size. I would love to have a small head in it so I am not running to house all the time, but not sure that is in the budget. I would certainly go with ten foot ceilings in most of it, but something higher in part of it to give overhead storage would be ideal. A room in back for spraying would also be ideal. If the funds were the, I would like to put in radiant heat in the floor as it is safer when using flammables, plus it simply makes everything feel so much warmer. I had not thought much about it, but the skylight is a great idea. Hit fifty last year and I need all the light I can get anymore. There is no doubt that putting dust collection and air compressor outside is the only way to go. Gets the sound outside so I can hear my tv while I work.
Thanks all for your thoughts. If the build happens in the next few months, I will be asking more questions.