Just some idea's:
Morrigan's.
Hand cannon.
Quests.
Legend cape. ( need to do few quests for it)
New prayers. (maybe you need to do hard quest to get it) (ancient prayers)
You need kc to enter gwd dungeon. (like in real rs)
Warriors guild.(for defenders)
Dragon defender.
Price checker in-game.
Some new skills like dungy,summoning,hunter and construction.
Webclient & highscores, would be awesome <3.
This are mine idea's,
Hope you like these.
-Mike.