If you accept that YJB has to be in the sie - and I don't think anyone credibly doubts that - then the question is whether the slightly keeping improvement that Buttler offers (and lets be realistic, he isn't Chris Read either) outweighs the loss of runs between Buttler and whoever loses out on a batting spot. I'm not convinced.
Nail on the head there, if Duckett/Ballance/Buttler are competing for one batting space it's hard to argue against selecting Duckett on current form. Would like to see Buttler playing as much red ball as possible with a view to getting him in, but that's much more likely when we're back at home and not picking 6 bowlers. Bayliss is clearly keen to get him in the side so wouldn't be surprised if he does play at some point this winter though!
Not relevant to the current tour, but Buttler playing at home would raise the prospect of our 4-8 being Duckett, Buttler, Stokes, Bairstow and Ali - that is some serious pain for away bowling attacks if the top 3 put a few on! And that's before you even get to Woakes or factor in how quickly Root scores.