I'd agree with you, I've acually come across two Brits in the UK on RRVs who have successfull sponsred partners (and babies) on a Spouse Visa and then the whole family has moved to Aus together.
The Sponsor can outline in their statement how the family intend to move together, both people can talk about their research into starting life in Aus together, etc etc.
I would think get the application in offshore, may well be granted by January and if not then it should be close enough for the partner to use an evisitor for the last couple of months, or just wait in the UK and fly over a couple of months after the OP.