Whether you think there are better implementations than the current one is not the problem, but rather that you are making a protocol change for something that miners are, by design,
False. There is no protocol change being proposed.
No, it is trivial to block 100% of them. A proposal to do just that appeared on the bitcoin-development mailing list yesterday from Peter Todd. This proposed change would relay
zero transactions with multisig outputs.
Most of the world is moving to P2SH for multisig, leaving the remaining "bare multisig" users mastercoin, counterparty, etc.