Bretton Woods:

USD is not based on QE. The USD is based on Fiat Decree. QE is the direct creation of currency by the Central Bank and the dissemination of this into the economy. This is only done at exceptional times (like now). The vast majority of created USD money is done through the banking system as debt so it is also accurate to characterise it as a debt based monetary system.
Question:
- Swaps 'linked'? You mean a Commodity swap - Wikipedia ? Why use a Swap at all? Why not just a Forward contract - Wikipedia for the commodity? What does using a Swap give you?
A Blockchain can be public or private. It can be under the control of entities (government or otherwise) or it can be public and under the control of no one. I think you are suggesting that users have to be authenticated which suggests some form of private blockchain or network of chains. The price of transacting is set by the system creators. It's not inherently cheaper to use a blockchain. The price is set by consensus - be that consensus public or private.
It seems also that you are saying that this system should be used by the states' foreign reserves managers. Unfortunately not all central banks or monetary authorities are independent and that means there will be some state control. Not all central banks are inidependent.
I see the core of what you are saying but I think some of the details need to be nailed down.
I have been observing banking systems for a fair few years and flaw within money based blockchains is the instability of free floating values. I have seen a number of ideas proposed (and haven't looked at it for a few years) but that problem remains open.
Goldman Sachs created
" Goldman Sachs-backed Circle goes live with currency-linked stablecoin " BUT multi-lateral pegging brings fixed rates and the world currencies need floating rates.
I personally think that the pegging could be done on a transaction basis (so the chain currency is more of a certificate than a fungible currency).
Interesting stuff.