Thanks again for even more suggestions!
I have reached out to Ice Castle to ask them a bunch of questions about the customizing abilities in their design. They are very willing to work with me in basically giving me a shell to work with and I can finish off the interior as my own project. They said "the shell will consist of a the walls, exterior siding, roof, treated plywood floor, exterior door and the exterior marker lights." They also mentioned that they do this for people quite often! I'll have a lot of work to do with electrical, plumbing, insulation, finishing off any interior walls and I'm sure a bunch of other things, but I love the concept of doing that on my own! They even sent me a couple pictures to show exactly. This idea looks like the best for the harsh winters as the full 2x4 construction of the walls will allow me to get a reasonable R-value if I use really good insulation. The really big question is if the campground would be willing to accept it?! I guess I'll have to contact them as well!
I'll keep you guys updated with whats going on and who knows, maybe start a new thread for a custom interior Ice Castle