18 nations seems like way too much, i think it will be hard enough to find that many competitive nations ...
Currently USA, France, Spain, Croatia, Germany, Argentina, Switzerland, Serbia, Russia, Italy, Australia, Canada and GB have at least 2 solid players, but Croatia (without Cilic), Switzerland (without Federer and Wawrinka), Serbia (without Djokovic) and GB (without Murray) might have a difficult future ahead of them.
Personally i like this new format because it increases the probability that german television will actually broadcast the Davis Cup, something that normally doesnt happen, especially since there isnt too much else going on in November (maybe except for winter sport).