The one who can issue money, can of course buy up the whole economy in the end. Whether this is by "backed" money, or "thin air" money doesn't really matter. The only advantage of "backed" money is that there will always be some finite supply of it, if the backing asset is a collectible, such as land or gold.
My analysis shows that backed money is indeed "out of thin air": As long as you have some spare asset, you can always issue money backed by them to buy more asset, and once you get more asset, you can issue more money, so the quantity of money that you can issue is only limited by the total available asset that you can buy in the whole world
To stop this kind of madness, it should be illegal to issue money backed by assets. If money can only be created by work or paying equal amount of valuables (for example exchange electricity for mining bitcoin), then that money will not create seigniorage
EVERY issuing of money causes seigniorage, it is unavoidable.
In fact, at first sight, the asset-backed method isn't so bad. It is when analysed deeper that there is a serious problem with it.
What happens actually with an asset-backed fiat, is that the asset is taken out of the economy, and stored in some safe, and that the corresponding value is issued in fiat. The trick of "buying more and more" can only happen if the asset against which the money is backed, is confiscated in some way, and then, the taking actually happens at that moment, and not at the moment of issuing the money.
What this procedure tries to establish, is a seigniorage-less monetizing of an asset. It isn't (at first sight) as stupid as it is presented here.
Suppose that people possess gold. Some have a lot of gold, other have less gold. Now suppose that the fiat-issuer (call it "the state") wants to monetize that gold, by issuing fiat backed by gold.
The state can now print a certain amount of fiat money, and BUY the gold from different people (giving them the money in return). As such, the gold that was in the hands of the people, is now in the central bank, and the fiat money that was printed by the central bank, is now in the hand of the people. The state cannot spend it a second time. The state now has gold, which serves as "backing" of the fiat money, and has taken that gold out of the economy.
At first sight, the state just monetized gold, and nobody got any seigniorage. People who got the fiat bills, gave their gold in place.
The state now has the gold, but doesn't have the fiat any more. There has just been an exchange of gold against fiat money.
However where this goes wrong is that the very fact of buying up the gold has increased enormously the price of gold. People who had gold before, had less buying power, than when they sold their gold for fiat, because the demand for gold, with this buying up by the state, has increased enormously over the normal demand of gold. So there HAS been a lot of seigniorage, and it went in the hands of those that possessed gold (which they acquired at a lower price than when they sold it at the state).
I took gold as an example, but you can take any valuable asset. You can take land, you can take shares in companies, just anything that has some value. By "buying up the asset with fiat" you *apparently* avoid generating seigniorage. In reality that's not true, because the increased demand (by the state) of the asset increases its price, and the seigniorage hence goes into the hands of those holding the asset when the state decides to buy it up.
Suppose that the state suddenly buys up Beanie Babies for freshly issued fiat. Beanie Babies which were at $ 50.-, will, due to this increased demand, go to, say, $ 300.- and people that had spend $ 50 on it, will make a 6x benefit which is the seigniorage. If the price would remain at $ 50.-, there wouldn't be any seigniorage, because for every $50.- fiat issued, $50.- of Beanie Baby will have been taken out of the economy.
The problem with asset-backed fiat is that the asset that is taken, increases in price. This is a disaster for the USE of the asset - so you better have an asset that has no use (but then, has no value!).
What the state does with that action, is to force a certain asset indirectly to become a monetary asset, but transfers the monetary value to its fiat counterpart.