Ah yes, I forgot:

5) In the European system, the top 2 used to get a week off before they have to play, so they have time to recover. The NRL could just juggle their system around a bit. Or something.

Correct.

Two weeks is the only way, because of each team's own post Grand Final celebrations, and because of the need to overcome the jet lag of the team that flies across the world on the Wednesday.

Nah. Club rugby switches off after the Grand Finals (some could say all rugby switches off by the amount of interest there is in the international game). They aren't called the Grand Semi-Finals- your WCC would either be a great event and detract from the grand finals, or more likely it would be a non-event that no one cared about.

Which would eat into the international calendar.

You win the SL to qualify for the WCC the year later. Just like in football. You qualify for the Champions League. And the winners of the Champions League qualify for the CWC after that. They aren't all in the same year.

What about
an actual tournament
top 4 super league
top 4 NRL

play in a mini tournament

1st plays 4th
2nd plays 3rd

so going off last seasons standing

1.St Helens v Sydney Roosters
2.Leeds Rhinos v Cronulla Sharks
3.Catalans v Manly Sea Eagles
4.Wigan Warriors v Melbourne Storm

A. 1 plays 3
B. 2 plays 4

A v B

yes very good idea