I have made some incremental progress on this and wanted to release our first vendored dependency of gRPC 1.13.1 since I was able to fix a good number of the import/code completion errors that Intellij was experiencing. I have published an example of what the jar/pom looks like in the Apache Staging repo:
You can also checkout and from a clean workspace run:
./gradlew :beam-vendor-grpc-1_13_1:publishToMavenLocal -PisRelease -PvendoredDependenciesOnly
which will build a vendored version of gRPC that is published to your local maven repository. All the projects that depended on the gradle beam-vendor-grpc-1_13_1 project are now pointing at the Maven artifact org.apache.beam:beam-vendor-grpc-1_13_1:0.1
I was planning to follow the Apache Beam release process but only for this specific artifact and start a vote thread if there aren't any concerns.