@ramsey I came to the same conclusion about the importance of an initial charter a few days ago in this message: https://externals.io/message/129300#129351
I think something that's different between this situation and the examples in your RFC draft is that the WG would be working towards a single goal, and most of its work would be released all at once when that goal was met.
That makes defining when the wider community is consulted trickier: too few voting opportunities, and the WG can spend months delivering something that gets declined; too many, and the WG becomes ineffective.