The only replaceable part of the club supporter equation is the supporter, we are not only replaceable, the club would actively encourage this scenario.
Legacy fan = (relatively) stagnant ticket prices and low matchday revenue potential
Nouveau fan = higher ticket price and considerably higher matchday revenue potential
The only role that legacy fans have that is of benefit to the club is the atmosphere, we are little more than extras in a TV production. Think of this the next time Pep, or one of the boys comes over to the touchline waving their arms exhorting an increase in volume from the fans.
As the old saying goes 'if you'll sup with the devil, use a long spoon'.