Currently, services are implemented by implementing an autogenerated interface (e.g. IMath). When a new RPC is added to to the .proto file, regenerating the code leads to breaking a build, because a new method is added to the serverside stub interface (which is quite natural behavior as such, but can be very undesirable at times).

A remedy would be to auto-generate an FooImplBase (naming TBD) that provides virtual methods with default implementation of all RPC returning just StatusCode.UNIMPLEMENTED.
If service implementation is inherited from the base class mentioned, adding new RPCs to the proto file does no longer break user's code.