I shouldn't need to do this forever, because, once I set up a reasonable assumption that I can keep this thing going (remember I'm the DEA, I just seized a shedload of bitcoins in a drug bust) it's in everyone's interests not to mine that block. They want to mine on top of the longest chain because everyone else wants to mine on top of the longest chain, but given purely rational economic actors who don't care about Bitcoin, that rule, like everything else, is up for sale.

Hell, I may not even need to spend any money - I just need to convince all these rational economic actors that I could and would spend that money if necessary, then it'll be in the interests of each individual miner to start following my rules, not Satoshi's.

Edit: "in the network's interests" -> "in the interests of each individual miner" to distinguish from the interests of miners in general, which are different here because it's a classic Tragedy of the Commons situation.