All valid points!
Not worried about climate control one way or the other...for me that is a non-issue.
It would be used entirely for storage and parking cars and a handful of bikes.
The garage on there now is 20x20, I'm sure I won't need a new garage any larger than that (anything will be an upgrade from our current, tiny one car garage).
I THINK the best option for adding the bed/bath will be to convert the existing garage. We have plenty of room to go back but can;t really go out on the sides.
Plus having the master bed/bath where the garage is currently works well for the layout of the house.
Keeping the garage the garage and trying to add on the master bed/bath somewhere else I think would be more of an issue.
Here is a pic just for fun...
As you can see there is plenty of room to move out from the existing structure.
Perhaps even enough space for a 3-car!
One can dream...