I would always say pick your best keeper but I fear when Bairstow is back they're gonna do Foakes dirty. Hope that's not the case, because he's still an excellent bat. Was often at the other end of those big chases last summer, and he's probably the best person in the middle order to bat with the tail...
Bairstow will surely come back in to the side, unless his injury proves to hamper him massively. But I don't think it should be at the expense of Foakes - at least not until we have seen how well Foakes handles the extreme pace of the Australian attack - there is great logic to picking your best keeper, especially when pouching a 50/50 chance off someone like Smith or Labuschagne might mean +/- 150 on the scoreboard, and as has been said, Foakes gives a different aspect to the batting line up.
That said, I'm sure who you do drop...Duckett would seem to be the obvious one, but its not like there is an obvious replacement opener, unless Baz is going to go really leftfield and say, in effect, our best six batsmen come in at two through seven, we'll just start with - for example - Broad and try and wreck the new ball!