Q. Can one ask someone else to do Kappores for him as a shaliach (agent) on a chicken?
A. Ashrei Hoish (O.H. 3; 7: 11) quoting Horav Eliashuv zt'l mentions that although one can name a shaliach to bring a Korban for him and thus obtain redemption and forgiveness, Kappores are different.
He mentions as other Poskim also do, that the main intention and object of Kappores, is to observe what happens to the bird, as if it should be happening to him. Therefore, it is a personal experience that only one can do.
Horav Shlomo Miller's Shlit'a opinion is similar
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a