Firstly I would like to disagree with suggestions that the World Cup be held every two years. It's the showcase. Making it every two years would devalue it, every four years is PRECISELY the reason side's WANT to win it, it's just 'not another trophy'
The World Cup of '92 remains the best format used for a World Cup Tournament yet. Although there is too many sides to re-introduce this format, it can be achieved with systems the ICC have in place.
I suggest a 10 team World Cup Tournament be implemented.
A second tier program (i.e. non-Test playing nations) should be encouraged, where they play each other home and away (much like the ICC one-day rankings) and gain ranking, the double benefit from this is that the regular play between them will increase their level in the hope of achieving Test status.
Meanwhile the Test teams continue their format, but the ICC take a slightly bigger take from the earnings to enable the second-tier program.
Every 4 years, 6 months before the World Cup Tournament, a World Cup Qualification Tournament is held.
Of the Test playing nations rankings the top 8 automatically advance to the World Cup, the remaining lowest ranked nations compete with the four highest ranked 2nd-tier nations in a round robin format, semi-finals, final format for the right to advance to the World Cup.
Then 6 months later the World Cup is run along the same lines as '92.
The World Cup is about finding the best, and to think that a side can win it without playing certain nations (i.e. say Australia at the moment) is ridiculous.
Round robin means you fight for the right to get there, and playing consistently good cricket against all nations involved.