The Mesh Sampler could have input (MyMesh) attributes like the mesh spawner.
PCG subgraph/graph`s attributes should have default values as well as actor parameters.
P.S.: A data/attribute struct or array would be also useful, that could be used in static mesh spawner.
For example a simple forest with one spawner node, but 3 kind of trees should be reusable by blueprint array parameter(meshes and weights).