Your tease excited me since I recently started grappling with this issue. Unfortunately, I'm underwhelmed. If the group deals only with binary decisions, participants have a single underlying competency, participation can be suitably restricted, participants don't have strong biases, decisions can be reliably assessed right or wrong, etc, then you have an elegant solution.

There are some clear advantages to histocracy over futarchy: most relevantly, I believe histocracy will work well on a small scale, while prediction markets require a large crowd. Given enough time and participation, histocracy will inevitably beat a market. There's less moral hazard, and less vulnerability to manipulation.

These claims seem completely unfounded. Prediction markets don't require a crowd. If implemented through a market-maker, you can get by with a single participant. PMs have issues, especially when used to make decisions, but this proposal is rife with manipulation opportunities -- accumulating competency and "spending" it to sway decisions, manipulating if a decision is counted as a success or judged at all, altering the order of decisions to accumulate competency or harm that of others, collusion to build competency of at least one individual (worthwhile since the weights are convex). The worse manipulation of prediction markets I'm aware of that wouldn't also apply to this is for traders to mislead others for later profit, which wouldn't affect the final probabilities used for decisions.

Besides PMs, there is work being done in Bayesian truth serum, peer prediction, and other collective revelation mechanisms that don't require verification of results for scoring, but still result in truthful answers.