Matthew 16:18 notwithstanding (admittedly a difficult verse for me, and the one on which a whole lot of this hinges), the protestant position seems more coherent to me. There are lots of things about your argument that aren't compelling to me:

- πρεσβυτέρους doesn't seem to me to be identified with "eachother" in the James passage, I'm not sure the interpretation of the word is relevant here.

- I definitely affirm the difference of roles. But "normal" confession is necessary for relationships of any kind to function. Catholics are positing that confession to God needs to be mediated, and fair enough, but James 5 doesn't say "through eachother" but "to eachother". But maybe this means James isn't relevant to the discussion at all.

- 2 Cor 5 says God has reconciled himself to us through Christ, and we're given the word of reconciliation — i.e., we're supposed to tell other people that they also may be directly reconciled to God through Christ.