Didn't Dish do exactly that when they were negotiating with TWC las time around?
Yes ... the channel was on for a few days and then pulled with additional promises made (it was to be replaced by a regionalized 24/7 weather channel that never came). I remain disappointed even though years have passed and I generally don't watch TWC (I did use the weather app on the receiver earlier today to look at the forecast).
I don't like broken promises - and while DirecTV has not promised that WeatherNation will be carried, making the channel available is on some level a promise. (Have they even announced the channel? I don't see a press release or see it on their package comparison page.) It is not something that millions will leave DirecTV over, but it isn't good to add channels just to be dropped.