Lack of accountability of the Representatives who have no constituents based on a community. Some say 'all politics is local' and to a certain extent that is true. Without the grounding and accountability to voters, either the House ends up as a debating society, or the States actually need to become stronger in many regards to backfill the influence of District representation. That may not be a bad thing, devolving to the States more real authority, (Uh, hmmm, and where is the dough to deal with that coming from?) however, an entire branch of government without accountability at the grass roots level strikes me as less representative, not more.
Good ideas are good ideas, and a more diverse public voice is in theory a valid concept. To me it seems that the Balkanization of the political climate would create more chaos and entropy, less ability to get anything actually done, and of course every good idea is
tempered by practical limitations. That is part of 'the art of the possible.'
So, with the "voice" of all manner of constituencies allegedly represented, the tyranny of the 'elitists,' idea men who don't actually have to get anything done, strikes me as more likely than less. I suppose the balance is that the Senate is the senior house, and the Judiciary would remain pretty much as they are.
An interesting idea, certainly, scrapping the State model of proportional representation, which would in summary create more noise, IMO, and get less done. Coalitions of remarkable collages would, on the other hand, be interesting to see.