You don't need to download a local wallet for namecoins to merge mine them. I just send mine to an exchange such as Cryptsy or BTC-e. I frequently Exchange them for BTC so I'm not worried about losing them if the exchange vanishes. Namecoins add about 1% to your total. DVC and IXC add virtually nothing and will never amount to much unless you're mining with multiple PH.
On the other hand, never use an exchange address for your mined bitcoins. Always use a local wallet.
How are you merge mining NMC? Are you running your own pool with your own custom code to do so? To merge mine any coin along with BTC, your pool must be able to call getBlockTemplate and generateTransaction for each of the coins you're merge mining. It needs to look at the current coin's block and see if the share being evaluated will solve that block. It's not just point to some wallet address, or you could merge mine every single SHA-256 coin out there.On the other hand, never use an exchange address for your mined bitcoins. Always use a local wallet.
I don't need to do any of what you said, the pool does it for me. Why are you trying to make this so complicated?
I mine on a pool (BTCGuild) that merge mines namecoin. I generated a NMC address on BTC-e and when my minimum payout is reached, BTCGuild sends the coins to the address.
. You're absolutely right. A number of pools already merge-mine NMC: Eligius, GHash, BTCGuild... probably others. All you need to do is supply your NMC address, which you can certainly do by creating one on an exchange like BTC-e or by downloading and installing NMC. Sorry about the confusion. 
