Yesterday there was a suggestion to get miners to blacklist the stolen coins. It is plausible Bitfinex might want to try and make this happen. It's possible some miners lost funds in Bitfinex also which may make this more attractive.
The hacker should have a couple of choices to prevent this from happening. They could either negotiate with bitfinex to keep say 10% of the coins or they can thwart blacklisting by getting the coins into circulation.
This will involve an initial haircut of 25% (30kbtc). Use a percentage of it to pay varying moderate/small amounts of approx 0.1 BTC to many of the most active addresses in Bitcoin to protect against reorg by getting them linked into transactions. Spend about 100 BTC on this.
Then they should create a series of nLockTimed transactions that pay 6 BTC in fees every 4 blocks for the next year for a total of 10000 BTC in fees. These transactions should pay large amounts (e.g. 50 BTC) to randomly selected active users from major Bitcoin forums spread out across the transactions.
This incentivizes the users to fight any blacklisting attempts and the hacker can pay themselves in the same chain of transactions.
I'm sorry for the losses of everyone involved and it's unfortunate to see two companies likely go down with this (BitGo & BitFinex) but it is essential that Bitcoin fungibility be preserved.
Any attempt to damage it needs to be thwarted.
Eh, I don't know. Personally it sounds like a good idea, but at the same time it seems like there are some issues presenting themselves. Namely the reorg. When applied as a fork, this shows that there is too much power with those who publish the forks, and as mentioned some people have already spoken loudly against it. I'm in favor of going against the blacklisting attempts, however I personally believe that a hack is a hack and in an economy like this where a majority of things are trust-based, nothing should be blacklisted and nothing should be reorged out of existence. If that was a thing, we could have done it with Mt.Gox.