Hmm... very nice idea, I like it.
Proposing a system like this is the easy part. How would you go about implementing such a system? I am sure the entrenched Demopublicans wouldn't go along with it, they would lose some of their control of the political machinery.
Well, sure. I mean, I just invented it (and I might not be the first to do so), and at the very least it would require years and years of discussion and refinement, not to mention implementation at lower levels of government, before we could even think about implementing it up higher.
I'm concerned that it violates the one-sentence-description rule.
Couldn't a system of at-large reps for large regions encompassing several states do similar things for small ideological constituencies? (I.e., if a given region has 25 seats in the House, then the Greens or the Libertarians only have to get 4% of the total turnout to vote for their candidate.) It would also ease pork barrel spending to some extent, because all 25 representatives are primarily loyal to an entire region, not one small district. I suggest this because I think the all-state jurisdiction of Senators has almost as much to do with their being less prone to that kind of stuff as their long terms and smaller numbers.