I would imagine in Thunder Road's case, its age and the removal of sealant paint factored into its early demise. Though if the park is that concerned with humidity, they could build the coaster with a steel structure similar to Invadr in order to reduce maintenance costs.
Anyways with rumors of Dodg'ems being moved somewhere else within the park, this is what I could see happening to the area in general:

2018-04-02 (1).png (1.5MiB)Viewed 3476 times
Dodg'ems' relocation opens up the area to become Project Alpha's ride plaza, and with the bathrooms in Carolina Harbor being located outside of the construction walls, I could see the area behind the new attraction becoming a new entrance to the water park.