Any number of All Blacks tests is an honour, whether you play 1 minute or 100 test caps. Sione Lauaki, Ben Atiga and Casey Laulala have played more for the All Blacks, than a majority of New Zealanders will in a life time. It would be a change that would undermine the value of playing for your country, be it New Zealand or Tonga. It would not solve any issues. Samoa, Tonga and Fiji are not short of any player quality. They have some of the naturally best rugby players in the world, and they have enough professional rugby players to be very competitive. What they are short on is preparation time and game time to build as a team. What the IRB need to do is give them funding for better facilities, coaching and windows for players to play for their countires. They need regular matches against quality opposition.
A quick injection of good players, isn't going to be a long term answer to anything. It's paper over the cracks. The PI problems comes entirely from funding, and having a few Australians and All Blacks will not solve that. I think smartcookie's idea is not a bad one, as it means that players will play for their country because they believe themselves to be members of that country. I would further add to that, and this may not be held with very much agreement, that if you represent another country, you give the caps you have earned representing another country back.