(As for the technical side - the issue seems to be that P2SH introduces a new interaction between the concept of "standard transactions" and the scripting system. Before, a transaction would be accepted if it was standard and the script returned success; now there's an additional requirement, which is that one of the standard transaction types now calls for you to rerun the script in a different way. This means that the "standard transactions" concept is now actually part of the scripting system, rather than a secondary sanity check, so it can't be fully dropped in the future. However, the special case is on the sender-script side, and I don't think allowing nonstandard scripts there was ever plausibly a good idea. I do still want to see the standard-transaction types broadened to include fancy tricks with time locking, but that's considerably less urgent.)
That's a good point, but it's a negative point. "Standard" scripts is merely miner bias. It's a flaw that the software developer is allowed to force his biases on miners, as it is right now, and making "standard" transactions a protocol thing would make the problem even worse. Miners are free to choose what transactions they accept on an individual basis, and work should be done to make that easier, not harder. That is, "standard" transactions should be undefined entirely. Eligius already will accept
any transaction, "standard" or not, without bias.
While I disagree strongly with the monarchial powers being given to Gavin, that is not the basis for my objection to BIP 16 specifically.