> capture your passwords
With public key auth, an attacker can't capture anything useful (unless of course they record traffic and later figure out a way to later capture the private key [1], but this isn't a problem that changing the port will fix).
> mimics SSH
You can't mimic the key files in /etc/ssh/ssh_host_whatever_key without root privileges, assuming these files are properly secured. So users will get an unexpected warning that the host key has changed.
> simple script that listens to port 2222
True -- in cases where something isn't already listening on 2222. But if sshd is started early in the boot process and listens on 2222, won't any script started as a regular user be unable to bind to the socket?