A ranking race. I already wrote this somewhere here. 4 years results in WCH, Continental championship, WGP/WL, WC and GCC decide who goes to the OG.
There would be no African teams ever for volleyball in the Olympics if we went with the straight ranking system and the IOC will not have that. Plus with FIVB trying to promote the game around the world, they will have to give a slot to the African qualifier.
So in a 12 team tournament, there is always a weak team in one of the two groups.
If we wanted to change qualification it could be like this.
World Cup: Host plus Continental Champions, World Champions and the next 5 top seeded teams regardless of region. Top 2 or 3 teams. Or it could be split into two groups of 6 with semifinals and final (if top 3 teams). Fewer games but more drama for the 3rd place match.
Combine the Americas into one qualifying group. South American with only 10 countries (really about 4-5 consistently play) has too much say. Could Argentina beat out Dominican Republic, Cuba, Puerto Rico or Canada for the 2nd or 3rd spot? Brazil and the USA would be leading contenders for the single spot.
For Asia to have a single qualifying tournament. Do not include them with the other European and North American teams. This would then allow smaller 4 team tournaments with other continents as your World Qualifiers after all Continents have played their tournaments.
Plus have the draws for the World tournaments be seeded by FIVB Ranking.