At the Rescue we often get pluckers who are wearing vests, or more often they are wearing sweaters. They usually look just like a sleeveless, turtleneck sweater, where their wings come out of the arm holes and the turtleneck is there to cover the area under their chin and around their neck and high chest area. And they usually are long enough that they cover their entire belly and you can just see their legs. And except for their wings, their backs and the tops of their shoulders are also covered. They actually work very well, and honestly I've not seen any bird wearing one who even acted like they had it on, like they don't even notice it.
The only time they care about the sweaters is on "changing day", which we usually do once weekly (unless they get them dirty somehow, with food or whatever). Some of the birds have multiple sweaters, so we always make sure that they have a clean one ready to put on, and others only have one sweater, so what we do on "changing day" is take their sweater off and throw them right in the washing machine, and then while we're waiting for their sweater to get washed and dried, we let them bath or shower, whatever they prefer, to keep them occupied while we're waiting. We also will take them outside while their sweaters are being washed and dried, because this tends to keep them occupied and not thinking about their feathers. Works really well. Getting the sweaters off is easy. Getting them back on is something that you just have to learn to do quickly and get it done, and then it's over, lol.
Honestly, the sweaters I've seen work really, really well. They allow their feathers to have time to grow back in, in some cases fully. And in some cases once their feathers grow back in fully (if they only pluck their chests/bellies/backs), we can actually slowly "wean" them off of the sweater. And it certainly does stop the mutilators from causing themselves harm...