In the 'Nothing to see here!' column, the selection of Amy Jones to keep wicket (one would assume) suggests that they are worried about Sarah Taylor's back... but they are always worried about Sarah Taylor's back, so there is nothing new there - she will keep in the Test!
Similarly, the omission of Anya Shrubsole hints at injury concerns there too, but I will be amazed if she doesn't play. (EDIT: Anya has said on Twitter that she will bowl on Day 2 anyway!)
The absence of Danni Wyatt and the inclusion of Georgia Elwiss, however, would seem to be significant. I had backed Wyatt to play on the basis of an ECB article; but a couple of people commented that I was reading too much into it, and there was no way England would play two spinners in Perth. It looks like they were right, and Elwis will play ahead of Wyatt.
(I think playing Elwiss makes sense too, and not just because of the spin/seam thing - Wyatt's skill-set is more suited to the limited overs game, especially her 'bish, bosh, bash' batting.)
My updated guess at the team for the Test would therefore be: