Tinkering around with Super League calendar options, I think what they need to do
14 team, 26 round home and away comp, no loop fixtures.
International weekend in June, they play France, or the highest ranked European nation.
Then 2nd could play 3rd and so forth - Scotland v Ireland, Wales v Italy.. etc. Easy way to do it.
No professional club games this week.
England playing in a 4 Nations European Cup every 2 years.
Regarding sub-internationals. I think they have their place. But the when how and why are important.
They have to represent something meaningful. They shouldn't take the place of real internationals. They should contribute to the game and the wider calendar.
State of Origin ticks 2 of the 3 boxes - I'd argue that Origin should be played out midweek in May and June alongside NRL split rounds, and that on an international weekend in July (pushed back a few weeks) Australia should be playing New Zealand.
Back to the UK - I think this could work:
England - excluding NRL players
vs
Celtic All Stars - best SL players eligible for Wales, Ireland, Scotland
-3 match series played alongside early Challenge Cup rounds, before international window.
-Gives England a competitive game
-Gives Wales, Ireland and Scotland players a bigger stage
-Legitimate selection trial for GB Lions tours for all 4 nations, not just England.
-Could be played in Scotland, Wales and Ireland as an annual exhibition.
Why not Exiles/Combined Nations?
Ultimately, they don't represent anyone, they don't have a higher purpose, it's just there to give England a training run. Who's cheering if Exiles win? Why should clubs risk players for a team without meaning?
Why not just play Wales/Ireland/Scotland?
It's a compromise. The unfortunate reality is that England v Wales is currently non-competitive. This is a way to give those national players a legitimate pathway and more higher level games, and still be an attractive enough proposition for England and paying fans. Splitting GBL into 'England v the rest' ties the two concepts together and gives a proper underdog angle. And, if England play in the European Cup, we get the best of both worlds.
A potential Celtic team
Lachlan Coote (Scotland)
Regan Grace (Wales)
Elliot Kear (Wales)
Ethan Ryan (Ireland)
Rhys Williams (Wales)
Joe Keyes (Ireland)
Marc Sneyd (Ireland)
Gil Dudson (Wales)
Michael McIlorum (Ireland)
Joe Philbin (Ireland)
James Bentley (Ireland)
Tyrone McCarthy (Ireland)
Morgan Knowles (Wales)
Danny Houghton (Scotland)
Adam Walker (Scotland)
Joe Wardle (Scotland)
Ben Flower (Wales)