In recent years, I have been thinking about a hypothetical solo FIFA World Cup bid for the People's Republic of China, and China is bound to make an excellent FIFA WC host if chosen (regardless of what controversies not regarding event infrastructure may arise). The 2002 FIFA World Cup, in South Korea and Japan, had the most venues (20), and the 1982 FIFA WC, in Spain, had the most venues in a single country (17), and if there's any country that deserves to match or beat cither amount, it would be the People's Republic of China. I could see them selecting at least 25 candidate cities for its bid. They wouldn't need Chinese Taipei, Hong Kong, or Macau. Ideally, I'd want to have ALL of the host stadiums be football-only, considering China having accelerated development of such stadiums in recent years, but I'd be tempted to add just a couple of athletics-track stadiums to the mix (Beijing, Shanghai, and possibly Nanjing and Kunming).
My idea for how China's bid would play out: Nothing fewer than 50,000. One stadium per city/metropolitan area. In the knockout stage (starting with the Round of 16), one match per city. China has a very large selection of metro areas, so it's the right country to pull this off. Here is the list of candidates, and (if listed) the matches I could see them hosting (all of the candidates can have no fewer than three matches total, including at least two group-stage games; venues for the quarter-finals can host three group-stage matches; semi-finals and third-place play-off venue host four group-stage matches; and the final venue hosts five group-stage matches):
Shanghai - Shanghai Grand Stadium (speculative) (100,000) - Final and the Opening Match
Beijing - Beijing National Stadium (80,000) - Semi-final and the Opening Match
Guangzhou - Guangzhou Evergrande Stadium (100,000) - Semi-final and the Opening Match
Chongqing - Longxing Football Stadium (60,000) - Quarter-final or Third-Place Playoff
Wuhan - New Wuhan FC Stadium (60,000) - Quarter-final or Third-Place Playoff
Nanjing - Nanjing Olympic Sports Centre (61,400) - Quarter-final or Third-Place Playoff
Shenyang - Shenyang Olympic Sports Centre Stadium (60,000) - Quarter-final
Dalian - Barracuda Bay Stadium (63,000) - Round of 16
Xi'an - Xi'an International Football Centre (60,000) - Round of 16
Chengdu - Phoenix Mountain Stadium (60,000)
Xiamen - Xiamen Egret Stadium (60,041)
Qingdao - Qingdao Youth Football Stadium (50,000) - Round of 16
Tianjin - Olympic Sports Centre Stadium (60,000)
Hangzhou - Proposed Football-Only Stadium (60,000)
Shenzhen - Shenzhen Stadium (45,000)
The following cities will need new stadiums for this bid: Kunming, Harbin, Changchun, Urumqi, Changsha, Nanning, Zhengzhou, Wenzhou, Xiamen, Haikou.
A few notes: Currently. Kunming's largest stadium only has a 35,000 capacity and is with an athletics track. Beijing's Workers Stadium is being rebooted into a football-only 68,000-seater, but I would lean towards using its National Stadium instead, with its more impressive scale. Shenzhen (provided they don't go with their Universiade Stadium) could be the lone candidate with a sub-50,000 capacity. Shanghai Grand Stadium is speculative at this point, but I feel Shanghai is deserving of a stadium with a capacity exceeding 80,000, especially with the existing Shanghai Stadium only being taken up to 72,000 seats after its current renovation. And we're unsure at this point if Nanjing, Shenyang, or Tianjin have any current plans for new large football-only venues soon; Their existing "Olympic Sports Centre" stadiums are just placeholders.
One last thing: If you asked me right now what MY choice for the opening match venue of any China FIFA World Cup would be, it's... Beijing. (Sorry, Guangzhou.)