i dont wear it like a backpack your right it would do my back in. instead i just lift it. you can lift it with one hand, then i just put it over one should to the front of the house, clean the front then pick it up and take it around the back and clean all the back.
Im only 23, so maybe its my age, but i have no problem doing this.
But if i used a van system for a huge house, or a secluded commercial premises i think your right, the van system would be better.