First, let's dispense with the idea that they care a great deal about money. They don't. The currency they deal in is power. Money is merely an aspect or symbol of that power. Losing control of it it is catastrophic to the way they currently do business, but if you look at the history of rulership, they're incredibly adaptable. In America, they have turned a nation of renegades and individualists into a sociofascist empire that maintains and appearance of liberty. So, looking to that, how might blockchains be incorporated?

One that I find obvious is that they can hide their legerdemain in plain sight. Instead of fractional reserves, they have an adjustable rate of proof of stake, based on some metric they control. It appears that all money creation is above board and clean... but they control the metric.

I could go on for a while on the ways they might subvert the technology while APPEARING to "fix" the economic system. If they can come off as heroes, then they elevate themselves and again appear to be the benevolent overlords.