Like it or not, a project like that is a huge undertaking. Much more than I certainly would like to take on. You have to at least give credit for all the work that was done. If the owner is happy with the end result, that's all that matters. Overall, I think that they did a nice job on that old bus.
I'll admit though, I thought the same as others here when I first saw the 2X4 framing throughout. Could've used 2x3 instead and 2x2's in some areas and saved some space and weight (although I agree that I doubt weight is that much of a factor in this instance). But that's just me thinking out loud after seeing someone elses completed project.