Hello Crazy Lover,
The lack of an ISO 639 code for modern usage of Ancient Greek is only one argument, and not necessarily one I put much weight on. The policy requires that a language have living native communities to read the wiki, and that is my personal position as well. There has been a lot of discussion on this list about this requirement recently, but no consensus on any change to it and no similarly objective workable alternatives.
The subcommittee does not make exceptions to the policy, so discussion should focus on the policy rather than on exempting particular requests.