I believed for a ban to have lasted this long isn't a temporary one, you still have some the courage of coming back after some year in making appeal, you sound being desperate about that account.
He should be desperate to get his account, why? Only because it was a Hero Member account and these days it is not possible for an average poster to attain such a level in a quick time. That's the reason he is appealing for the account to be unbanned.
Now to the OP, there are hundreds of accounts that were ban because of plagiarism and older than 5 years time. So if they unban OP and give him special attention, they would need to unban all others too
So, the account will never be unbanned especially if it is banned due to plagiarism.