It would be a good learning experience for everybody involved if the core dev team did indeed release a new version of the client that did this.
I don't believe this requires an immediate change in the client software, does it? Simply the software used by the miners would need to be changed to not incorporate transactions spending from the locked addresses. Eventually I suppose it should be incorporated into the main client software, but that is not the main priority.
Anyone who feels their coins have been unfairly locked, because they weren't part of the Mt. Gox wallets, can just provide proof of ownership to the appropriate group to have the addresses removed from the locked list. Clearly this would require good evidence, but that can be arranged and weighed appropriately.
This shouldn't inconvenience many people at all, at least not the honest ones, and would prevent either insiders at Mt. Gox or the alleged thieves from being able to move these coins until the facts are resolved.
When the bankruptcy is cleared up, which I understand will likely be a year or more, then the coins can be unlocked. Obviously, not something we would want to be doing for every theft and problem, but perhaps something to consider when major problems affecting substantial sums are involved. In fact, the ability to perform such a lock under extreme circumstances can be considered a strength of Bitcoin.
There is nothing wrong with the Bitcoin community, as a consensus, saying they want to be just and support law enforcement in such cases. In fact, I would argue it is using available information and the capabilities of new crypto-currencies in a freedom supporting way.