If you only want to read the geometry data in you packaged build, then cache it when building your custom mesh (we are doing this to dynamically paint explosion damages into a vertex color channel and we need the distance between vertices and explosion’s center).
If you want your geometry to be fully dynamic @ runtime, UStaticMesh is not a good option. I guess it is possible to go fully dynamic by packing you positions into OverrideVertexColors, then use this into your vertex shader with some crazy material hacks. Do you need more info on this?