The ITF's preference for a neutral venue for both finals has been met with strong resistance within the game.
The proposal needs to be approved by the national governing bodies at the ITF AGM in August so there remains a possibility it will not go ahead.
The ITF is also looking into including the Fed Cup semi-finals as part of the same event to enable the World Group to expand from eight to 16 teams, bringing it into line with the Davis Cup.
All other rounds would continue to be played on a home-and-away basis, but that will not placate the doubters.
Australian player Sam Groth wrote on Twitter: "Have the @ITF_Tennis lost the plot with these @DavisCup reforms?"
Combining the two in November will also increase the length of the women's season, with the Fed Cup final currently taking place two weeks before the Davis Cup final.
The status of the Davis and Fed Cups has been undermined by the growing absence of top players and ITF president David Haggerty has made reforming the competitions a priority.
The reduction of men's singles matches from best of five sets to best of three will also be voted on in August and should pass comfortably.
More than 20 cities expressed an interest in hosting the event, with Geneva beating Copenhagen, Istanbul , Miami, Turin and Wuhan from a shortlist of six.
The venue in Geneva would be the 18,000 capacity Palexpo, with the matches to be played on a hard court.
The ITF argues that a fixed final would maximise commercial and media interest while removing the current difficulties governing bodies experience in trying to find a suitable venue at short notice.
The extra revenue would be put towards increased prize money, player participation incentives and worldwide tennis development.
Haggerty said: "The creation of the World Cup of Tennis finals is at the heart of a series of reforms that represent the most significant changes in the history of Davis Cup and Fed Cup.
"Change is needed to ensure that we maximise the full potential of these iconic and historic competitions.
"We've consulted widely and listened carefully, and believe we will deliver an exceptional new event for fans, players and nations."
Winning over leading male players will be crucial, with the ATP potentially further weakening the Davis Cup by exploring plans for its own tennis World Cup backed by Barcelona defender Gerard Pique.
Meanwhile, the inaugural Laver Cup, a Ryder Cup-style event backed by Roger Federer's management company and Tennis Australia, will take place in Prague this September.
