I am not an expert, but here's what I can contribute, culled from reading:
Some people do feed chicks, or other types of rodents of appropriate sizes. A big corn snake can easily take a smaller rat as a meal. I won't put my opinions in because I don't have enough expertist to make them useful. I have also read tha some picky eaters get "stuck" on a food item, and if it's hard to obtain, such as brown mice only, that could be an issue unless you have a mouse colony.
As far as the raw piece of chicken, I know there is one breeder who successfully includes chicken in his corns' diet as a major item and his corns look gorgeous & reproduce well.
Now you are going to get a piece of n00bie opinion. Anything to tempt a snake that has been on a prolonged food strike! If that's a glob of raw chicken, sobeit. Next meal the mouse can be wrapped in raw chicken like a rollup. And if the snake is an excellent eater, one unbalanced snack of some sort probably won't hurt it either, even if it is a piece of raw chicken meat.