I am not convinced that ring fencing is the only way to protect player welfare.  I think that there are far more creative options available that would also (probably) even out the Premiership.

Firstly, I would be in favour of increasing the Premiership to 14 teams and having a 2 up/2 down approach.

Secondly, I would scrap the Premiership trophy.  It is pointless as there are now only 12 teams in it and there is too much of an imbalance between clubs playing development squads and clubs playing their full strength squads.  Scrapping this cup will free up enough weekends to play the extra 4 premiership games needed.

Thirdly, I would introduce a mandatory number of games that each player needs to be rested for through the regular season (i.e. ignoring play-offs).  E.g. Each player would have to be rested for 8 games of the season.  This would help with player welfare and introduce an interesting dynamic to managing the squads.  I would introduce a simple penalty system along the lines of - each team who has not rested a player would be deducted 4 points per player/game at the end of the season.  I think that something along these lines would be transparent and easy to police.

I think that the third item would also help to get the academy players playing in the first team as, with injuries, international call-ups and rest days, most clubs will be short of players in key positions.  This would really give younger players the chance to step up and get regular game time.  But, the key point is that all clubs would be in the same position.  Also, the important thing is that all games are meaningful, no matter what the % of fringe players in the starting 15 is.

For the play-offs and Euro competitions, teams would be able to use their full complement of players.  The resting of key players would hopefully mean that English clubs have a slightly better chance at progressing through to the Euro cups finals.

[edited - spelling]