The fact that the seller could steal any deposit made by the buyer makes existing accounts a non-negotiable resource which cannot be traded on exchanges like the currency itself.
The large scale powerbrokers don't need liquid markets to offer to buy up the supply of mining accounts, because they are the market makers. They simply publish an offer and the sellers come to them.
You are simply forcing renting instead of outright sales, but you can't stop sellers and buyers from pursuing that which generates the most value for both of them. Again I urged you to study the economics.
To beat the consensus, you'd have to make a special deal (providing the required security guarantees) with the majority of currently active account owners whose number will be increasing over time.
Such a scenario is much more unrealistic than just buying (old) private keys of a handful of stakeholders who had majority power over consensus at any point in the past.
If new accounts are growing fast enough to render old accounts irrelevant, then the power-law superior "investor" buys more new accounts than everyone else.
Perhaps they can even devise a way to buy new accounts that have their chosen private key which the seller has never seen? Do you cryptographically force the creator of a new account (minter) to sign the private key (and can this be done without revealing the private key)?
No cryptocurrency can exist in a threat model where an attacker can simply hack the majority (or a significant number) of users to steal their private keys and do any kind of evil things.
There is usually assumed to be an orders-of-magnitude difference between the number of users of a system and the number of mining accounts.
I don't know how you plan to gain billions of adoption from users and also expect then all to invest in interest bearing tokens and perform mining duties. There seems to be a mismatch in incentives between what would entice billions of people to use a coin and investing. Most people aren't investors, else we would not have a power-law distribution of wealth.
Also with PoW, the miner isn't locked to one private key. His mining equipment is orthogonal to any cryptographic key. And this hacking issue is one of the security problems for PoS in fact (especially when most of the coins might be stored on an exchange).
Granted, but my consideration to your first statement applies here as well.
What?
Furthermore, if you assume that the majority of users engage in collusion, then it's pretty certain that every user will get to know about it, which enables them to create an honest fork of the chain, leaving the bad guys behind.
Investors do what is rational. Investors are not users because most people can't be investors (they don't save enough).
Fungibility is nothing more than the economical property of a good or a commodity, that any unit of is equivalent to any other unit. Existing accounts (with a non-zero balance) pose a financial risk to the buyer. This risk depends on the person of the seller and requires individual arrangements between the parties to be mitigated. Therefore, any account must be considered an individual good which contradicts the definition of fungibility.
Renting eliminates that fungibility barrier.
The goal is not to create an asset that no one wants to buy, but to create an asset with limited use cases. You (mainly) buy an account because you want to invest your money and receive interests. Once you have an account, you will also have an incentive to use it for minting as you could finally sell its children, while your minting costs would be very low without PoW. However, as shown above, you don't have an economic incentive to buy and use multiple accounts for the sole purpose of minting since the discounted cash flow from selling child accounts would be (at least asymptotically) lower than the acquisition costs which must be regarded as sunk costs as no market for existing accounts will exist.
If you think that this reasoning is flawed, then please point it out in a precise way.
If ROI from minting is so much lower than interest, then why will anyone bother to mint and mine? Vitalik pointed out that altruistic prime is not stable for an undersupplied public good.
And since you've made the return from honestly minting and mining so low, i.e. you have created a power vacuum, why wouldn't it be an incentive to rent or collude to earn more from that aspect of the assets, such as for example if the TPTB want to blacklist some transactions (some dissidents or enemies) without destroying the value of the ecosystem.