While car storage is not a priority (or even in the next 5 years), it is great to discuss it. As for Restrooms, that is the next project on the list, with the dirt work coming shortly, from my understanding. But with the dirt work, comes the initial grading that will be the start of the whole new expansion process.
As for design of the building, the Plastic skylights would work for light. I have seen several storage buildings with them in the roof and they are not that noticable. Several companies make the style of building we are looking for, for a reasonable amount of money, which may or may not include erecting it. I'm sure with some leg work, a company can be found that will do everything from the frostwalls or whatever is required to completion of the building.