It's simple - a regular, annual tournament whereby the European nations play off against one another. If you want to see how that'd work, google 'Six Nations'.
As has been said repeatedly, people who are not already RL fans *do not care, and do not understand why they should care* about Warrington v Widnes. It's two teams from places they've never been to and likely never heard of playing a game they've rarely watched. It's really easy to say 'we should fix the club game', much harder to make it happ. And while we sit around in the hope that a sensible reorganisation of the club game miht happen, we are getting outcompeted in our biggest growth area (Internationals).
There needs to be:
-Yearly 5N tournament in high summer (England, Scotland, Wales, Ireland and France)
-End of season 3-Test tours (v New Zealand, Australia or a combined 'Pacific Islands' side)
-Fixed international eligibility rules so you can't leave Samoa or Tonga for NZ or Aus, or the home nations for England.
-Early season match against The Exiles (although RFL should actively approach the Barbarians to take over this match and get the Baa-Baas brand into RL)
-Yorkshire v Lancashire series.
This wouldn't be a success overnight, it'd require a hell of a lot more games to be played away from the Heartlands, but it'd provide a regular series of games that would have a big enough crowd and media draw to warrant greater attention, sponsorship etc.
It would also disadvantage bigger clubs more likely to suffer from International / Rep call ups, but given we want as competitive a SL as possible I don't think it's a bad thing if Leeds were to occasionally lose at Belle Vue as had 6 players away with England.