A relay contract for upgradable contracts

Relay.sol

contract Relay {
    address public currentVersion;
    address public owner;

    modifier onlyOwner() {
        if (msg.sender != owner) {
            throw;
        }
        _
    }

    function Relay(address initAddr) {
        currentVersion = initAddr;
        owner = msg.sender; // this owner may be another contract with multisig, not a single contract owner
    }

    function changeContract(address newVersion) public
    onlyOwner()
    {
        currentVersion = newVersion;
    }

    function() {
        if(!currentVersion.delegatecall(msg.data)) throw;
    }
}