Warehouses do not gather resources, they pull resources harvested from company owned farmhouses within it's massive radius.
Why would it matter how close you build one warehouse to another company's? It makes sense for farmhouses, you are literally contesting a small radius of resources.
The building restriction should only apply to your own company. Currently, only one company (whoever builds a warehouse first) can build a warehouse on a island as the restriction radius takes up 1/4 of the size of the standard island. Furthermore you limited players even more on this with the requirement to build a warehouse near water (why?).
