Great post, JR. I think it's important to note that while you do present a compelling argument for bitUSD through your comparison with fiat USD, this is simply setting the stage. You make a subtle yet important point where you said, "The holders of bitUSD retain allodial title to one dollar's worth of bitshares - a cryptoasset with a fixed supply."
So, not only is the bit asset backed (potentially over collateralized in some perspectives), but its protocol (another sources of value) carries the fixed supply parameter. Obviously, this just skims the surface but clearly there is a lot of potential in bitUSD.
Agreed that bitusd is more than the sum of its parts (literally). Good points. The motivation for this series is to set the stage for how cryptoassets can function as money and whether a community is better served by monetized debt or monetized equity.
A question beyond the scope of this post is how a medium of exchange is implicitly backed by the innovative technology it relies on. E.g. blockchain is potentially more valuable of an innovation than ACH transfers.