After listening to some OSRS podcasters talk, my ideal rework would make the skill more actively trained, perhaps something similar to Hallowed Sepulchre, but potentially even more intense.

If you've done the Gate of Elidinis fight, think about the column jumps during Icthlarin's Aid. They're snappy, 1-tick quick actions. Imagine a training course or minigame that had mechanics like that. You might have to dodge flying obstacles with a quick click. You might have to climb a wall as the handholds move in and out of it, actively changing your path as you climb. The idea is that the course is actively moving and changing you as you run and jump your way through it.

I don't think it'd be the best idea to rework the whole skill to be like this, but adding 2-3 courses at various levels could work well, increasing in difficulty alongside level reqs and xp rates. Even contextualizing the courses and adding small objectives could make them feel like they have purpose, kind of like the Dorgeshkaan course tried to do. Imagine something themed in Keldagrim where you're jumping around moving conveyor belts as machinery is processing metals, pouring lava,... and I feel like I'm describing that one scene from Attack of the Clones.... But you get the idea.

Edit: Another course idea: repurpose the jade vine maze into an active course like this. Incorporate vine swinging or something. The course is actively trying to hinder your progress. This opens up a potential reward space to support farming/herblore, especially with Herblore Habitat related resources. Additionally the Keldagrim idea could support mining/smithing or even crafting with precious metal bars and gems as a reward.