It seems to me that economic rent, far from being an immoral oversight, is the fundamental law of capitalism. In all cases a capitalist seeks to charge more than it cost them to produce an item, or to gain some information, or to acquire a property. The more that item, or information, or property is worth to the market, the greater rent/profit the rentier can extract.
While this function can clearly be abused by those with great means, the basic concept is exactly what makes capitalism so efficient when it comes to growth: any person has the chance (hypothetically) to find and exploit differences in cost and value to increase their personal wealth. I can't find anything immoral with this form of rent-seeking. Which seems to imply it isn't so much the practice that we hate, but who chooses to practice it. When the laborer exploits, he makes a living. When the banks exploit, our whole economy shifts. We applaud the former and fear the latter, and that fear appears to be the motivator behind most criticism along the lines of that in your paper (apt criticism).
But, fear aside, there is no effective way to control inequities of power. If you cap access to power too low, you rob your economy of potential growth. If you cap access to power too high, the cap is meaningless: the powerful will circumvent your laws and do as they wish. And no matter how you cap it, the real effect will be to entrench the current elite and prevent new blood from cycling into the upper echelons (which is to say, you will have institutionalized inequality). Those currently in power will simply find a way to conceal or transform their power and rule in a shrinking market of rivals.
All of this is to say: inequality is an issue of power, not money. And in that context, inequality is a law of nature. If our goal is ending inequality in nature, we are wasting our time. If our goal is unseating those currently in power, we need to be honest with ourselves about that. In the end, questions of fiscal inequality are about power (a real force), not morality (an imagined one). While power can be taken, it can't be destroyed. And if we take fiscal dominance from the powerful, that dominance will just take a different form.
tl;dr What we're really grappling with is fear of nature, inequality being a natural and unavoidable result of differing degrees of individual and collective power.
Really enjoyed the paper, and I'd love to see these principles tested in the coming years. Any plans to develop the blockchain protocol you described anytime soon?