I'm still not following. It's definitely still prep. You're just doing the prep a day or two earlier. But you can do that with any water bath by prepping, stashing in zips, and sticking them in the fridge.
I think I see the value of being able to start a cook at 2PM as opposed to sticking to things that can run all day.
Most of the things that work really well in a water bath also hold really well for a day at temperature. I think you're right to feature white meat chicken in your marketing copy, because that's one protein that is iffy at long temps, but I can't think of much besides that (and eggs) that I'd worry about holding at temp a few extra hours.
I wouldn't let a fillet steak (or a hanger, for that matter) in a water bath for 12 hours, either. Or consider chicken thighs: We cook the best thighs in the world by taking them through a temperature curve. When we have the time, we cook them at 57C for 12-18 hours, and finish them at 63C for 1-2 hours. The end result is silky, sublime, but still firm.
On prep: It's not prep if you don't to put yourself up to it. It's not a chore, it's 10 seconds while the coffee machine heats up. Our idea is that reducing the need to do things, the friction, you'll end up doing them more often.
I think I see the value of being able to start a cook at 2PM as opposed to sticking to things that can run all day.
Most of the things that work really well in a water bath also hold really well for a day at temperature. I think you're right to feature white meat chicken in your marketing copy, because that's one protein that is iffy at long temps, but I can't think of much besides that (and eggs) that I'd worry about holding at temp a few extra hours.