Did you read BIP 16?
So there is no manipulation allowed AT ALL.
A maximum of 1,000 "naked" OP_CHECKMULTISIG operations are allowed in the scriptSigs and scriptPubKeys of transactions in any given block.
We had a block earlier this month with 1,8000 scriptSigs, so I think we are uncomfortably close to that limit.
BIP 16 "hides" the CHECKMULTISIGS in the serialized script, so more of them are allowed.
At the very least BIP 17 is harder to test-- Luke had to test on the main network because I was naughty and wrote and ran a BIP-17-transaction-stealing bot (sorry, I couldn't resist).
I have zero commercial interest; I am not being paid by anybody for anything right now.