what would be entailed in getting a native (macos) arm64 version of grpc_python_plugin built?

https://grpc.io/docs/languages/python/quickstart/ But replace

pip install

with

pip wheel

. Hosting that wheel is of course another thing.

You can then specify where to find that wheel via the options in https://www.pantsbuild.org/v2.16/docs/reference-python-repos.