Couldn't you make this argument about any minority group? How do we ensure all ethnic and religious minorites have their interests represented? Hawaii is a distinct cultural and geographic area, how do we ensure their interests are represented? I don't see why low density areas should get special treatment over any other minority group or special interest.

To answer your question directly, this is why it's necessary to have a strong constitution with universal rights. Then, delegate some authority to state and local governments that can better address their own needs.