So if Leeds were to get a couple of weeks warm weather training before the game, it would presumably have to be before the SL season starts, which would be January. The NRL clubs dont even start playing pre season games til February, so they wouldn't agree to a match that early. Unless you're suggesting that Leeds take a few weeks out of SL just to prepare for the WCC? The only other way is to play the game as now without a couple of weeks 'warm weather training', but would Leeds really be happy to play a SL match on Friday, fly down under and play a WCC game in Oz the following weekend?
Until a clear gap in the fixtures on both sides of the world can be found, we'll have the WCC in this country annually with the NRL clubs treating it as a glorified trial game.
I don't see there would be any problem playing the match in May or at any time to suit the Aussie's. It's been moved a few weeks later into the SL season to suit the Aussies, so our club has to play a mid week match. Makes no difference if the WCC is played in SL Round 3 or round 13 to be honest. Clearly if the match was in Oz, the SL club would need to juggle two fixtures to allow them to travel , but that could be achieved.
A club like Leeds would build their season around peaking for the WCC, Challenge Cup and play-offs.
The reason it doesn't happen is because the Aussies can't see any short-term benefit in it for them.