This is an interesting idea. Unfortunately I can’t think of the right way to do this. The spline percentage in my example is more of a Get and not a Set. The only way to have it scrubbable is to use that Take Recorder trick you mentioned.
I can think of a gross workaround using a custom event in the Sequencer track to find a percentage point on the spline and set the actor transform there, but that’s something you’d have to key every frame potentially.