There should be a conveyor belt system, where English youngsters work their way up the ladder in England, then earn a move abroad (they can always return).
Take Will Hughes as an example at Derby. If Derby get promoted this season, he should want to spend 1 season with Derby where he knows he'll get regular football. Then move to a bigger Premier League team, again where he'll expect regular football (Swansea/Newcastle maybe?). As he keeps improving, he earns another move up - maybe a club on the fringes of the top 5 or 6, like Spurs or Southampton. Then to a Champions League club (or Liverpool
), and once considered a star players, why not move out to mainland Europe? Learn new tactics, learn a new language, learn how clubs in Europe work.
The exceptional talents may jump up more quickly - but they still must endeavour to play regular football at the highest level they can. If this means loan periods in the Championship, or lower Premier League teams, then that is better than playing U21 football.