With regards to the insulation foam on the underside of the metal sheeting, you could have some problems with discolouring and breakdown after a few years if you use a cheap one. We have just built a garage and used the insulated sheeting that had a lining under the insulation. Probably more for cosmetic reasons but looks a lot better that the exposed insulation.
Large windows on all sides will mean that it is not energy efficient even with being open.