Rigging a Morph Between 3+ Keys

I’m a 3D artist trying to get started with ToonBoom rigging and I’m wondering if there’s a way to interpolate between multiple drawings (ie. 3 or more) similar to the way that shape keys/blend shapes work in 3D. Basically I’d like to have a base drawing and then a bunch of different versions of it, each with a certain weight that determines how much it influences the final result. The most ideal solution would be a node that I could plug multiple drawings into, and then each drawing would have a slider that controls how much it influences the final output (sort of like the switcher node but with interpolation).

I’ve messed around with morphing a bit but it looks like you can only morph between two images, and only on the timeline. Right now I’m thinking I can at least make a rig to morph between two drawings by creating a morph on the timeline and then controlling it using a retime node, but I have a feeling that that might not be the best way to go about it.

The ultimate goal for the rig is to be able to create a fire flickering effect on the shadows cast onto a still character, so I’m also open to other suggestions on how to create that effect. Right now I’m thinking of having three keys of the shadow in different places and then morphing between them. I tried using a compositing setup that would expand and contract the boundaries of the shadows, but that didn’t give me enough control over the direction the shadows moved in and also caused them to bleed over the character’s outlines in a way that was difficult to correct unless I turned the effect down really hard.

I’m super comfortable with the concepts of scripting and nodes so feel free to go crazy with the suggestions.