“every power that goes to Scotland must be matched by the same power coming to England”.
Sounds perfectly reasonable to me. Although if 5 million Scots are entitled their own parliament then the English regions, representing a total of 50 million people, are entitled to theirs too – not just one English parliament in London.
Unfortunately the Tories won’t like that idea and Labour have always been pisspoor on the need for an English parliament never mind English regional parliaments.
Edit : TBF Labour did give the North East the opportunity to move in that direction, so I’ll correct myself on that last point.