All great questions, and I'll preface my response to saying that the true answers to these problems would have to be addressed in the "industry-specific brainstorming" that I mentioned. The results could look wildly different based on the problem the blockchain is addressing.
That said, the movement of "tangible assets" to "blockchain assets" is without a doubt a huge challenge for blockchains, but usually only when dealing with "real things" vs "systemic things", eg exchanging fiat for cryptocurrency. Integration into a private blockchain can be wholly systemic (so system-to-system vs reality-to-system). Integrating a new company into the system could be done by a joint effort between the members of private blockchain (who are all incentivized to help, because it's in their interest to ensure that no member of their industry goes unchecked.)
The economic incentive to commit to PoW is intrinsic to the adversarial network itself - basically, the desire of a company to survive the zero-sum game (success in such is typically measured by market share.)
To revert to a centralized authority is not an invalid approach, and may very well be the "happy medium" that allows this concept to solidify into something feasible. However, it is a "half-in, half-out" solution and is still vulnerable to corruption.
This is -of course - all speculative, but my overall point is that the discussion to reach solutions to these challenges will not be had if blockchains are written off as "dangerous nonsense".
That said, the movement of "tangible assets" to "blockchain assets" is without a doubt a huge challenge for blockchains, but usually only when dealing with "real things" vs "systemic things", eg exchanging fiat for cryptocurrency. Integration into a private blockchain can be wholly systemic (so system-to-system vs reality-to-system). Integrating a new company into the system could be done by a joint effort between the members of private blockchain (who are all incentivized to help, because it's in their interest to ensure that no member of their industry goes unchecked.)
The economic incentive to commit to PoW is intrinsic to the adversarial network itself - basically, the desire of a company to survive the zero-sum game (success in such is typically measured by market share.)
To revert to a centralized authority is not an invalid approach, and may very well be the "happy medium" that allows this concept to solidify into something feasible. However, it is a "half-in, half-out" solution and is still vulnerable to corruption.
This is -of course - all speculative, but my overall point is that the discussion to reach solutions to these challenges will not be had if blockchains are written off as "dangerous nonsense".