Cloak banshee would basically mean you have only marines out on the field. Marines are pretty terrible to deal with the blink all-in. So while the Banshee would be nice it doesn't provide the same level of zoning the tank gives you. And since banshee do nice DPS but not fantastic having one shelling away on blink stalkers means your marines will get raped then your mineral line will get raped in the process. The cloak would wear off far before you could really thwart the all-in. I'd imagine the best use of if you go cloak banshee would be to send it to your opponent's mineral line and try and stop more stalkers from getting produced while making bunkers at home.
I'd also have to run the timings but I think it would be really hard to push out cloak as well.
I'd also have to run the timings but I think it would be really hard to push out cloak as well.