This would be my way of doings things. For qualifying, I would combine the Asian and Pacific qualification process as opposed to previous qualifiers. And then I would guarantee one team from each region. Then based on how the other teams in each region go in qualifying, I would allocate 4 Repechage spots. For this there could be 4 Repechage qualifying pools of say 4 teams. So lets take an example.
Lets say from this world cup the Pools end up finishing like the following (just random guesses):
Pool A - Australia, Wales, England, Fiji, Uruguay
Pool B - South Africa, Scotland, Japan, Samoa, USA
Pool C - New Zealand, Argentina, Georgia, Tonga, Namibia
Pool D - Ireland, France, Italy, Canada, Romania
So through go the Australia, Wales, England, South Africa, Scotland, Japan, New Zealand, Argentina, Georgia, Ireland, France, Italy.
Then the regional take place. Lets say the regional qualifiers are:
Europe: Romania, Oceania/Asia: Samoa, Americas: USA, Africa: Namibia
Then you take the next best four teams from each region. So for example (based on what we saw last time):
Europe: Russia, Portugal, Spain, Belgium
Oceania/Asia: Fiji, Tonga, Hong Kong, Korea (I assume the other Pacific Nations wouldn't mount a big challenge).
Americas: Canada, Uruguay, Chile, Brazil
Africa: Zimbabwe, Kenya, Madagascar, Tunisia.
Then you allocate them a Repechage Pool based on their World Ranking. Do this in a random draw. So the tiers for these pools would be similar to that of the actual World Cup Draw.
So according to the rankings today, the tiers would be like this:
Tier 1: Fiji, Tonga, Canada, Uruguay
Tier 2: Spain, Russia, Chile, Hong Kong
Tier 3: Korea, Belgium, Zimbabwe, Kenya
Tier 4: Portugal, Brazil, Tunisia, Madagascar,
So for example the Pools could be:
Pool A - Fiji, Hong Kong, Belgium, Brazil
Pool B - Canada, Russia, Korea, Madagascar
Pool C - Tonga, Spain, Kenya, Tunisia
Pool D - Uruguay, Chile, Zimbabwe, Portugal
These games can be played at a random venue - possibly in Japan this time around as they are hosting the world cup. Then the winner of these Pools each go through to the World Cup. Then when you want to expand the tournament to 24 teams, the top two from these Pools will go through.
Finally, when everyone has qualified, the draw will for the World Cup will be done. This can be done a year before the tournament and when everyone has qualified. The rankings of every single team can be taken into account, so teams like Fiji (who are ranked 10th in the world but probably won't gain automatic qualification) can be put into the 3rd tier for the draw.
I hope this isn't overly complicated haha.
- - - Updated - - -
A bit of a tangent but related.. I've always thought the world cup should be a bit like the Sevens. At the end of pool play you have the main cup tournament but then also split into a plate playoff. It would keep the smaller nations involved in the tournament and give them more exposure and keep there fans interested. Some of the equally matched tier 2 countries could put on some cracking games - would be good to see Samoa v Tonga or Georgia v Romania, Japan v England played on the world stage.
I like this idea, you could play the games midweek while the quarter finals are occurring. It would also be a better way of deciding the automatic qualifiers as opposed to 3rd places in the pools.
So you'd do the exactly the same thing for quarter finals except, 3rd replaces 1st and 4th replaces 2nd. So for example in this tournament you could potentially get plate quarter finals like:
England/Australia/Wales v Japan/Samoa
Japan/Samoa v Fiji
Italy v Tonga
Georgia v Canada
And the teams that get to the semi finals of the plate would get automatic qualification for the next tournament. It would also be a revenue builder for World Rugby and we know how much they love that haha