Apart from it would be more places to OSRS gold walk about and find experience. To start I might suggest a fresh set of hills with a city on the top coated with snow ( I think it'd be cool since there arent any of these ). To present this new town jagex could earn a pursuit where adventurers heading into the mountains suddenly disapared and probably it was some monster.
Thus you would go to these mountains and find a town with a few king who thought adventurers were spies trying to steal his gold or something (as the town would be prosperous with golden mines).
Also, in order to enlarge the map we can add another new realm besides the one mentioned before. This new realm could be located after the mountain move (which could be very harmful by the way) or in a huge island such as karamja. But you are most likely thinking" what will be the story behind this area?" .
So... to be able to get that you would also have to begin a pursuit. At the first place captain Ned in draynor will tell you that there are stories of sailors finding a island which isnt from the maps but are afraid of going there. Your mission is to go investigate! When you get about the island you figure out people are diferent (cause they are japanese or chinese runescapians). This way we could also add samurai and ninja armour to the game as reward from the quest. I am hoping that you guys like my thoughts about this and please don't hesitate to give your opinion! Or, in case you've got a diferent and better idea please let me know.
This is part of my own Mining mini-game idea. I thought this idea was good enough to be in a seperate forum. If you would like to see my Mining mini-game forum, please go here. Whenever your pickaxe's pick head flies off, you are left with a pickaxe handle and the select head which you lost. Imagine if you're able to change the pickaxe handle, but keep the pick mind. These distinctive pickaxe handles come in various sizes, shapes, and buy RuneScape gold colours.