Every risk becomes a cost and lowers the ROI. You really need to understand economics.
That's true, but there's more to it in my design. 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.
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. Please refer to the chapter "Heartbeat transactions to achieve objective consensus" where I explain this crucial difference to traditional PoS currencies.
So your coin becomes centralized via hacking and there is no resilience for the coin to recover from it. (The hackers drain the hacked accounts, so those accounts become permanently unfunded and inactive, so the remaining active minting accounts are centralized.)
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's no point in developing a Bitcoin killer based on that assumption IMHO.
Also your mechanism does not prevent renting an account whereby the owner proxies the desired activity of the renter. It also doesn't prevent collusion.
Granted, but my consideration to your first statement applies here as well. 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.
You can't defeat thermodynamics. There will always be a flaw when you attempt to tell nature that a fungible resource is not fungible. The low entropy of the resource is not obscured from nature.
No. 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. I don't see how the laws of thermodynamics should affect this.
It certainly is possible to create an asset that no one wants to buy and thus there is not point in discussing a design that will have 0 investment and security.
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.
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.