For there to exist no power vacuum, then the value of mining (I didn't write just minting) must always be much lower than the value of interest even for someone who centralizes control over mining. Which obviously can't be true. Logic fail.
I found that the only way to solve this problem was to make it implausible (nearly impossible) to do the bad things that control over mining can do
by incorporating Byzantine fault detection and combine this with unprofitable mining, so only those who have an incentive to maintain the Nash equilibrium actually mine (so that the risk cost of attempting attacks is far too high because it isn't cost-free to try over and over as it is in the nothing-at-stake of PoS[1] and the chance of succeeding is very low due to the Byzantine fault detection).
So that in a nutshell is my design solution. The technological challenge is in the details of accomplishing it.
Note PoW transfers the security cost to the environment as waste heat, electric utility companies (and to a smaller extent the ASIC hardware and infrastructure providers). My design transfers the security cost as a gain to the investors of the coin, i.e. a form of interest gain. If we assume that in both cases those gains ultimately percolate up to TPTB, then they are equivalent in that respect other than the losses to waste heat in PoW.
[1] When PoS doesn't become PoW due to the stake grinding competition.