Firstly, it’s great that you try this. This is indeed where Ragdoll is going, but it isn’t there yet.
At this time, there simply isn’t one. Ragdoll can add physics to existing animations, like a tail or the transition into physics from the impact from a bullet etc.
The Live Mode tools is a step in the direction of animating using only Ragdoll, yout intuition here is solid and you’ll see more of this shortly. But the current version is not it; all examples you’ve seen of Ragdoll were animated using traditional rigs and posing techniques with Ragdoll added over it.
It’s fine to assign to the IK bones instead. See: