That would make a great soft wash hauler. Be sure to get a spray in liner on that one. That will rust out quick with no protection. Line X I believe is warranted against sodium hypochlorite.
I will be real curious how this trailer works out for you. I thought of the same concept for our part of the world, since we have old man winter to deal with.
I like the idea of easy access to your tanks, but the security and neatness of everything else being inside.