I thought about all these mechanisms before and I came to the conclusion there is no way to have decentralized physical backing for a crypto-coin.
Inside the GEC economy, anyone may spend entire
exacoins to themselves at
anytime; however, to do so would be to make everyone quintillion-aires, for others would soon follow suit. (In other words, it is the reality of others "following suit" that, ultimately, regulates the inflation of the GEC economy.)
Sorry, individuals don't prioritize the effects of group action over their near-term individual gain.