Would the majority of the miners have to upgarde to a BIP 0011 compatible version of the Bitcoin server before we could use this functionality ?
Yes.I'm testing patches against the last two versions of Bitcoin (0.3.23 and 0.4.1) for BIPs 11 and 12 right now to make it as easy as possible for miners to support them. Review or help testing is very welcome:
https://github.com/gavinandresen/bitcoin-git/tree/v0.3.23_op_eval
https://github.com/gavinandresen/bitcoin-git/tree/v0.4.1_op_eval