Tracking / backing to a market index or something like the SPY ETF could be a welcome addition to “always a dollar” and the unbridled volatility and speculativity of crypto(coins|shares).
The benefit is that it is banked on the crypto side of the fence. And for such a currency, perhaps NuBot would not need to keep the tightest spread possible, introducing a source of revenue to Nu.
Some thoughts should go to determine whether a candidate stock index / ETF should be rooted in a country that is cryptocurrency friendly, as likely something that tracks to a financial market will attract a lot of interest – from all types of people and agencies.