I think Brad will go with this line-up until it doesn't work anymore.
I am not sure if Hayward and Brown really care (probably a little), but it also doesn't seem quite fair - especially to Brown. If we had come out at the start of the year with Baynes/Brown starting then we would be running essentially the same line-up that we did all of last year (before the Kyrie injury). This proved to be successful.
Hayward clearly wasn't ready to start in Oct and this seemed to cause a ripple effect on some other players, like Brown. With the more offensively inclined Morris starting, it makes more sense to balance him out with Smart. If Baynes were starting, it would make more sense to balance him out with Brown. And Hayward is a recent All-Star who is finally coming back around so he should probably start, too.
If things start to falter a bit (Morris comes back down to earth, Smart punches another picture frame), then I would expect to see the opening night line-up back in place; but, until then, we seem to have a nice balance that is working.