What about objects, mobs or recipes that require multiple skills, and might give XP to several skills?
We already have that with combat, and arguably the new fish alchemy (need 50 cooking to hold a fish, use for alchemy or cooking).
What about mobs that need knowledge of Wizardry or Alchemy to defeat? Golems needing geology (Mining) experience to hurt properly?
Dissecting things for Cooking and Alchemy XP?
Requiring not just construction, but forging to create some furniture? And giving XP to both?
Fungus kills giving a bit of Fungiculture XP, or requiring it for drops?
Destroying furniture for Strength XP, or placing it as target dummies?
Shortcuts requiring a certain skill to pass like in RPGs? (but no Agility skill -please-)
Fishing drops giving non-fishing XP if the drop is not a fish?
It could feel rewarding to level up several skills in anticipation for an activity that requires both, or rewards both. I loved levelling fishing to X, cooking to 50 to be able to use swordfish in alchemy. A bit of depth without too much complexity. What do you think?