The premiership is too big. There are too many clashes with club and international matches, too many matches where the winner is known beforehand, and barely any thought given to player welfare - physical and psychological.
The gap between the Premiership and the Championship is too large - mostly as a result of the war that PRL has waged upon the Champ for the last couple of decades, with their biggest coup being to insist upon stadiums of 10k.
In England the ideal set-up is 10 teams in the Premiership, and 14 in the Championship, with 2 up and 2 down each year (or 1 automatic, and 1 play off) and much less stringent minimum standard requirements - but requirements that do extend to the management / ownership of the clubs actually being able to afford to play the season. For example, the reason for the 10k requirement is to receive a certificate from the local council, but there's absolutely no reason (well, protection racket) that the same requirements can't be applied, just scaled down to a 3k stadium.
There should also be a cup competition including all the clubs in the Prem and Champ, and the 2 leagues should be managed and marketed as one. You can ring-fence at that level if required, but even then, it should have built-in regulations for kicking out, or bringing in teams every 4th year or so - based mostly on both on- and off- pitch performance.
Granted, I wanted to reduce the Prem via relegation, not bankruptcy.
UK or European leagues would be a disaster for Rugby in the UK / Europe.
There's plenty of room for different structures in England, France, Ireland/Wales/Scotland and Italy.
European Cups should be 16 teams at each level
SA have nothing to do with Europe or European rugby, so I wouldn't shed a single tear if they had to learn how to negotiate with their SH "neighbours" without just throwing their toys out of the pram and sulking.