Before the full time professional era

of sport, players used to migrate in the off season of the domestic competition to play in the club competition elsewhere internationally. English footballers came here to play with St George and Balmain and Parramatta among others in Rugby League. I remember in cricket that Sir Garfield Sobers famously played for South Australia - in fact did he captain the side? I'm not sure. Anyway this migration of players improved the game through the transmission of skills and tactics. Others clubs improved their skills against the prowess of the international import and so when the international match would occur, the host national team found that its players had developed skills commensurate with the visitors'.
Shane Warne and several other Australians have been giving of themselves to international clubs - Warne has made this possible on account of having withdrawn from the one day team - but to my knowledge we are inviting few if any imports into our Pura Cup or whatever the interstate competition is call these days. As for our League players, they elect to spend their retirement years in international clubs by which time it is rather late for the competition over there to develop defensive skills against a not quite has-been.
International Soccer has developed on account of the migration of players through the clubs competition and the benefit to Australian Soccer is obvious with our having made it into the World Cup finals this year. If Australia wants to remain on top in the Cricket, then it should retain the current policy of not importing internationals to play in our domestic competition. But we should not be surprised if crowds fall off and interest wanes as the result becomes ho-hum. And we should not be surprised further if Cricket the Game dies.
To revitalise world cricket, there needs to be a system by which players in order to be eligible for international matches must have contributed to the world game by having played say ten matches in the domestic competition of another country. Dutchmen and Canadians might need to start off in Metropolitan Grade but give them a few years and they could be pushed into State Cricket. It depends on what we value the most - winning now; or having a game to play in ten years time.
As an aside but by way of summary, look what happened to the Tri Nations crowd in Brisbane last Saturday - the biggest crowd in 30 years on account that Great Britain had socked it to Australia in the previous game and so they considered there would be a match worth watching.