i'll confess that i don't understand this.
leaving your client running 24/7 is an invitation to a hack. you know -- port scanners?
and what's the difference if your pooled mining proceeds show up in your wallet more or less instantly? they're in the blockchain. that's all that matters...
i mine pooled. i open my client maybe once every two or three weeks. from the account of a separate user with an extremely restrictive firewall.
Having a port open on a specific range above 1024 forwarded to a single machine on your internal network isn't that damaging. I've done it for my entire career on the internet, with proper internal security measures in place.
(Up to date OS, anti-malware, virus-scanning. Not to mention 'safe' data-handling for any unknown binaries.) Also, I don't know of any current exploits that could use port 8333 of the bitcoin protocol as an attack.