Here’s the thing. When we meet Frank he’s already spent a year dealing with Trapper’s hedonism and Blake’s apathy… so he’s on edge. He’s a good-to-great surgeon in ideal conditions, but conditions aren’t ideal at the 4077th. He’s feeling the stress.
He only manages a bit more then 5 months under the combined weight of Hawkeye and Trapper. They eventually break him and he goes home on a medical after losing 40 pounds and breaking out in hives all over his body.
So when do you start casting?
Already started, it’ll be an animated MASH. It will do for MASH what the live action Cinderella movie did for Cinderella… retell a story that’s already been told a million / billion times and doesn’t need retelling, in a slightly different way.