Sell Friday entry first then Wed and Thurs entry as extras. They could also link the Wed/Thurs entry to coach or Worthy View packages and open the car/camper van fields later.
Totally and I don't envy them. There is plenty of room on site for the amount of people but it needs a complete logistical redesign, they need to reconsider the amount of complimentary tickets that are seemingly being given out and their booking policies need a rethink.
Increasing the cost of it for the average punter shouldn't even be a consideration as a solution to the problem however small the increase.