i have some cpu in different location.
For the moment the built in miner assigns new addresses for each block from the wallet where the client is running.
You could take a copy of an encrypted wallet and distribute to all miners. That way you will be guaranteed that the addresses assigned will be only the range of addresses that are in that specific wallet. As long as you do not unlock the decrypted wallet, the keypool will not refill.
There are however, for the moment no way set a fixed address to where the reward is sent. It's easy to modify the code to do that, though.