They should just dust off the plans for what was Jazz Land
. Turn Charlie and the Chocolate factory into a shoot the chute ride, add in an indoor ride (coaster?) in the vacant land to the west. That helps with noise abatement, if nothing else.
Jazz Land was a nice idea for that end of the park. Looking back at the plans now it seems like it would have been ideal to use the theme from Hex or the history of the Towers across several rides. With Thirteen being built in the years since, though, I don't know if you could stretch the whole Dark Forest idea across too many rides.
It'd be worth it, though. It is strange that given the park are named after the Towers, so little is made of them and the myths around the parks history. Looking at the then proposed indoor ride for Jazz Land, maybe it was meant to be a haunted house. That'd let you demolish the old one, use a bit of the car parks behind it over in Gloomy Wood and expand the Forbidden Valley end of the park for the Big Thrills coasters.