When we say "financial assets" what we actually mean is claims and liabilities. When you own goods, no subjects existe with the liability to provide you something nor you have claim towards the subject, because goods in themselves have tangible benefit. But when you own a financial asset, which have no tangible benefit, such subjects exist. And you own a claim towards them. In my OP I gave the examples of liabilities in the case of fiat, stocks or bonds and subjects (borrowers, company, bond issuer) that have these liabilities. In case of newly issued banknotes by the central banks, subjects are commercial banks or governments. That's because new banknotes are issued as loans to said subjects. So, the bases for financial assets are liabilities of actual subjects. And every holder of the financial assets has clam towards these subjects.
That's pretty much what I was talking about when I mentioned "ownership of debt".
On the other hand, holders of blockchain quantities have no claims to actual subjects, given that no subjects with liabilities exists when new quantity is put into the blockchain. So no financial asset exists behind blockchain quantities. That's why without new investors voluntarily accepting the quantity, holders have nothing.
In fact there are claims and liabilities. The owner of the private key for an address who sends bitcoin to another owner owns a "claim" of the BTC over the other person, who holds the "liability".
What you are actually saying is that my investment in blockchain quantity is backed by my own investment(my fiat reserves)
Yes.
...which is obviously nonsensical. All that I and prior investors did, was paying off the existing members of blockchain. Our funds didn't end up as reserves for our blockchain quantities, but as spending of old investors.
Even though the only thing happening was the nodes writing the transaction on the public ledger, that does not mean that funds are not moving around as reserves. Bitcoin completely abstracts this concept because its own protocol has no concept of financial reserves, which also happens to be the reason why random new cryptocurrencies have almost $0 market value when they are listed. It is the process of listing the cryptocurrency on an exchange that enables the exchanges themselves to attach their financial reserves (their own users' cash) onto bitcoin, hence why every exchange has a slightly different price.
This widget on Google that we call the "BTC price" is not an aggregation of all these prices, it is nothing more than Coinbase's BTC-to-USD ticker.
Spending of old investors' money, by itself, does not imply that those investors are not getting claims to their spent bitcoins (or liabilities for their bought bitcoins).
It seems you didn't get what the liabilities actually mean in financial assets. The absence of new investors is the best way to explain this. So, you have a stock and no new investor is willing to buy it from you. Does that mean you are left with nothing? No, because the company has the liability towards you and that liability is called equity. Equity is paid to you either as dividend or buyback and liquidation value. In bonds, it is the bond issuer who has the liability towards you and that liability is called principal. In fiat borrowers and banks have the liability. Borrowers must use quantities that you hold to pay off the debt which is why they are forced to exchange their goods, services and labor with you. The banks must liquidate the loans with issued quantities, which is why in the case of borrowers default, banks have the liability to exchange foreclosed property of borrowers with your quantity. After all, deposits are explicitly stated in the balance sheets of the banks as liabilities.
So whatever your interpretation of claims and liabilities is, it is completely wrong. Because, in the absence of new investors no subjects exist that have the liability to provide something to the holders of blockchain quantities.