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thinking of loans outside of the feeder club system, which I'm assuming for chelsea only exist to get round the issues of getting UK work permits for young players from the EU/Rest of the world.
Not sure where your assumption comes from. Chelsea’s academy is largely English. Loans are used to bring in players after the academy. Many loans are to European clubs. Vitesse has seen more than most but is not unique.
Loads of young English players from Chelsea are on the continent. Vitesse has played a large part.