I don't think a one nation rule is the solution. A place like Fiji is never going to have the population to support a competetive rugby league team using just domestic players and those who aren't quite good enough to play for Australia and New Zealand. It's better to have Hayne, Uate, T-Rex, etc., playing some games for minnows than none at all IMO. A blanket rule is not the way forward.
The most important step that needs to be taken is to allow players to represent minnows AND play State of Origin. If this rule was implemented there's every chance guys like Neville Costigan and Josh McGuire would still be playing for PNG and Samoa, respectively.
Beyond that, I'm not sure. Perhaps a sliding scale, teams outside the Top 20 can use x amount of players who have previously played for top tier sides with a minimum of x amount of domestic players, going lower as teams ascend in the rankings. That way as teams ascend through the rankings, sides like Italy can slowly be weaned off their dependence on imports and the quality of domestic competitions can only be improve by using the domestic players. To just flat out say guys like Mini cannot play for Italy is handicapping ourselves.
But then again, that could just lead to yoyoing up and down the rankings as teams get higher and have to rely on more domestic players.
Whatever the solution is, it's great to see so many fans passionate about the international game. And on the upside, although it's sad to see Russia going down by 84, it's a positive for Italy to be winning by such a big scoreline.