Great question! I actually have built a poc that is not released yet. It's on the roadmap. It requires some tooling for the devs building these plugins like a CLI for building the WASM binaries, bundling, manifests, etc.
The current poc still has significant performance overhead, and that overhead grows as the plugin system becomes more powerful. If plugins are only allowed to apply a WGSL shader, the performance impact is almost negligible. But features that require broader access to timeline data, such as time shifts, speed ramps, or full timeline transformations, become much more expensive and make zero-copy architectures harder to reason about.