Here's another format: Commitment once a year. Top 8 nations play in the same city in two round-robin groups. The bottom two nations - the last in each group - get relegated into World Group 2, and the Top 2 finishers in World Group 2 are bumped up to the main World Group, and so on and so on down the Groups - So if 56 nations are involved, there could be 7 cities in Fed Cup action at the one time. Because the nations for the Groups will be decided by the end of the week, cities for venues could be determined in advance.
USA, Slovak Republic, France, Slovenia
Belgium, Russia, Japan, Italy
WORLD GROUP 2
Sweden, Romania, Germany, Austria
Hungary, Canada, Australia, Switzerland
If Slovenia and Japan finish at the bottom of World Group, they could replace Germany and Switzerland in World Group 2, who would then go up to World Group. The bottom 2 nations in World Group 2 go down to World Group 3 and so on.
Good or bad idea? I actually came up with this about 8 years ago as an alternative for the knock-out format.
Does any of that make sense?