Animation C# Jobs: Any way to blend on top of existing RuntimeAnimatorController?

Hello,

I've been running into a particular hurdle trying to add procedural adjustments to a model after the animation step. I was hoping to create a system (sort of like an IK), in which the armature can be adjusted for a custom height and length, and update it after the animation, but before the IK system kicks in.

At first, I tried hooking into LateUpdate+FixedUpdate, so that the animator has already been evaluated by the time my system starts. This works, but I've been having a difficult time with jittering, in which I concluded the culprit was the execution order of my procedural system.

So I gave up on that idea, and looked into Animation C# Jobs, which was a glimmer of hope for me.
I was able to hack together an AnimationJob script that did fundamentally the exact same thing.

Here's part of it, where I additively apply a vector to the position.

Code (CSharp):

1.         void ModifyHeight(AnimationStream stream)
2.         {
3.             // Apply height adjustment to all bone-relative up directions
4.             Vector3 pelvisPosition = Transforms.Pelvis.GetPosition(stream);
5.             pelvisPosition += Transforms.Pelvis.GetDirection(stream, Vector3.up) * Height;
6.             Transforms.Pelvis.SetPosition(stream, pelvisPosition);
7.            
8.             Vector3 neckPosition = Transforms.Neck.GetPosition(stream);
9.             neckPosition += Transforms.Neck.GetDirection(stream, Vector3.left) * NeckHeight;
10.             Transforms.Neck.SetPosition(stream, neckPosition);
11.         }

It works, but I noticed that the animated bone positions were being replaced by the AnimationJob.
Not the intended result, in which I need the character to animate the height-adjusted bones from an existing Animator.

I've been looking through the documentation on Animation Jobs and Playables, but I haven't been able to understand much.
I've been playing with

AddInput()

and

Connect()

, in hopes that I can connect the output of the Animator PlayableGraph to the Job graph here, but no dice.

Code (CSharp):

1.         private void OnEnable()
2.         {
3.             pony = GetComponent<PonyCharacter>();
4.             animator = GetComponent<Animator>();
5.             m_Graph = PlayableGraph.Create("Pony Animation");
6.            
7.             if (!m_Graph.IsPlaying())
8.             {
9.                 // Create the animation job and its playable.
10.                 animationJob = new PonyModifiersAnimationJob()
11.                 {
12.                     Pony = pony.pony,
13.                     Transforms = new PonyTransformStreamHandles(new PonyBones(pony.anchors), animator)
14.                 };
15.  
16.                 m_ScriptPlayable = AnimationScriptPlayable.Create(m_Graph, animationJob);
17.                
18.                 // an attempt with animator blending, but I haven't been able to figure it out.
19.                 // ...
20.                 // PlayableGraph animatorGraph = animator.playableGraph;
21.                 // PlayableOutput animatorOutput = animatorGraph.GetOutput(0);
22.                 // Playable animatorPlayable = animatorOutput.GetSourcePlayable();
23.                 // m_ScriptPlayable.AddInput(animatorPlayable, 0, 1);
24.  
25.                 PlayableOutput output = AnimationPlayableOutput.Create(m_Graph, "output", animator);
26.                 output.SetSourcePlayable(m_ScriptPlayable);
27.                
28.                 m_Graph.Play();
29.             }
30.         }

Is it possible to use AnimationMixerPlayable or AnimatorControllerPlayable to add the outputs from the Animator PlayableGraph and the AnimationJob together?

I hope I'm not insane for thinking I can do this