Strikes me the problem is your federal supreme court sticking its nose where it doesn't belong. All legislatures in Australia barring the Senate are one vote one value, but that's by their own choice (and was a little controversial in Western Australia when they recently changed). If you ask me, it's important for every state or country to determine its own constitution without anyone else sticking their nose in. Doing so is likely to cause resentment and political collapse in the long term. It's already happened once in the US... 
 :::::You could save it from being so stupid by using proportional representation, especially if you decided seat size was fixed—so that each county elected n members, where n depends on the county's population size. How do Americans feel about proportional representation btw? In Australia most of the arguments against it only make sense in the context of a parliamentary system (albeit Tasmania has used PR—the Hare-Clark system—to elect its lower house since time began).  
 :::::IIRC the US senate was appointed by state Governors until the early 20th century. Have the state upper houses always been elected, or where they appointed at some point? Could they be appointed in the future? 
 ::::: ()