I like it too. I think it will blend nicely with your existing dock structure. Only issue I see is if you limit the base to 28 ft wide the top floor can't get much over about 16 ft wide or you will lose the look of this architecture. I would also note that in the pole structure that Eddie posted it is structured in a way that I too would have used OSB decking instead of plywood because the rafters are used more like purlins. This allows you to screw directly into them to hold the sheet iron on.
