I fail to see the "private blockchain" aspect of what you are describing above. What's the difference to colored coin / token approaches such as OMNI and XCP?
I don't think there's a difference. Except it will be possible to bulk multiple blockchains with one transaction per confirmation.
The main point is to reduce the load on bitcoin itself while being able to use the security it provides. Still There's a need for trusting the owner to keep the blockchain alive. But good part of it will be that the owner will not be able to double-spend without performing 51% attack on bitcoin.
This is a rough idea. I think it can be valuable.
"Private blockchain" Meaning a blockchain that's privately owned by someone. And at least private key is needed for producing new transactions for adding confirmations.
I would like to gather better technical description for it.
One of the important reasons that re-org exists in bitcoin. Is that no one would be able to kill it. By creating an invalid block at tip. This will be possbile for these private blockchains. But only one person is responsible for it. And all users can monitor it.