
New International Cup Idea
It would make the World Championships more tedious, if not exciting, that's for sure.
I think FIBA's pursuit of 3v3 competitions is more in line with what you're suggesting - not that I think this is more exciting or entertaining than traditional rules. "Unique and new" =/= better.
How do you mean [FIBA] are going down the Soccer Path? From memory the world cup is structured very similarly to that of FIBA's world championships, but obviously on a larger scale.
Soccer also acknowledges the risk of fatigue and injury of playing international tournaments by only allowing <23 year olds to participate in the Olympics + a veteran captain. THIS is something FIBA/Olympics committees have been considering.

...but why?
What exactly about the current international tournament(s) format doesn't work, which this idea solves?

Australia currently has the Oceania qualifier series against NZ, the World Championships held every four years and the Olympics held every fours years. Then there's the Olympic qualifier tournament for those countries that aren't seeded, other regional (international) tournaments, international friendlies and practice leading up to these events etc.
It's worth noting that the qualifying tournaments for the Americas and Europe would be much more intense than the AUS-NZ series.
I'm assuming that your cup idea would supersede some of these events, but keep in mind: the players do have jobs. With the risk of injury already weighing into every decision they make, why would they subject themselves to another tournament?
Olympics, World Champs, or 'New International Cup': which ones do we actually care about?

