I don't see the value in keeping infected birds, survivors or not. That's how disease is spread. It sure does not work with ILT. A bird who survives ILT is something to be removed because all it does is pass on the disease horizontally. While you may think you're breeding resistance into chicks, in the meantime, you are infecting other birds by passing it horizontally. Nah, no thanks. I'll cull sick birds. The ones who don't catch whatever is it is, in my opinion, are the strong ones, the ones with the best immune systems. That is more logical to me.
As you well know ILT, and Marek's are not the same thing, so they should not be treated the same. The problem with Marek's is that, by the time you discover it's in a bird in your flock, it has already passed horizontally, and beyond. You can cull, treat your entire property, and wait 5 years to bring in new chickens. Usually with a few disinfection treatments, and a 5 year waiting period, your property is then free of it, however, there is no guarantee. Remember, the contamination area is typically a 5 mile radius, so wild animals, summer breezes, storms, etc. will spread the microscopic dander very quickly. Not only is your property contaminated by the time you discover it, but neighboring properties too.
When you discover Marek's in your flock, your entire flock, and usually your entire property is already contaminated, not just the birds in immediate contact with the one(s) you've discovered have it. A better alternative to culling everything, treating the property, and waiting 5 years, is to close your flock, and begin breeding the survivors. You already have a closed flock, so continuing with your birds would be easy for you, and in short order, you would have a highly resistant, to totally immune flock, and all generations thereafter.
When reading about the virus, don't just read the manufacturers claims, but read the research. There are a lot of maybe's, possibly's, and on some strains, the research plain out states the vaccines simply don't work. While the manufacturers tend to claim the dander from vaccinated chicks, when they're mixed in with unvaccinated chicks, or chickens does not usually cause Marek's in the others, the research says otherwise.
I agree it's better if you don't get it, but if you do, this is one of the few diseases that it's not better to cull for, but rather continue breeding the survivors to reap the benefits.