Jagex could make the game more difficult by eliminating the majority of teleports or making them harder to use beyond hub for teleportation . The map of the world has become smaller because of the many Teleports.
It is a great idea to greatly increase the size and variety of all things. The more wild the areas are and the more immersion we would be in the world of adventurers that traverse from high civilization to lowlands. The map will appear small when it is within a reasonable draw distance. Jagex could make important changes to improve this.
Restructure mountain ranges. Currently, we have a handful of mountains that are influential: those east of Varrock and those to the north of Burthorpe and those to the that are south of Al Kharid, and those west of Ardougne. Making rivers and the like flow easily from these mountains would make them feel more real.
Make the forests great. It's much better. That includes the swamps. These areas will feel more wild when they are further from civilisation. I'd play for 1.5-2 hours each days during the summer to gain 50k of defense experience. Although it was short , it was challenging to sign up and gain this experience since I wasn’t in the moment.