I believe that Satoshi expected most people to use some sort of lightweight node, with only companies and true enthusiasts being full nodes. Mike Hearn's view is similar to Satoshi's view.
I strongly disagree with the idea that changing the max block size is a violation of the "Bitcoin currency guarantees". Satoshi said that the max block size could be increased, and the max block size is never mentioned in any of the standard descriptions of the Bitcoin system.
IMO Mike Hearn's plan would probably work. The market/community would find a way to pay for the network's security, and it would be easy enough to become a full node that the currency wouldn't be at risk. The max block size would not truly be unlimited, since miners would always need to produce blocks that the vast majority of full nodes and other miners would be able and willing to process in a reasonable amount of time.