I am not on the committee, just a lurker. I find the Golang proposal/design doc approach amenable to the expected scope of work.
Another benefit of the GitHub approach is greater participation by non committee members.
> GitHub allows for Git-based workflows, and there's prior art related to
> language design we could steal ideas from, for instance:
> - https://github.com/fsharp/FSharpLangDesign
> - https://github.com/rust-lang/rfcs
> - https://github.com/golang/proposal
> - (any others noteworthy?)