But the whole point of your response was based on the possible security breach of the trusted node. None of the 1–3 would even be necessary if we posit that the nodes are fully trusted, ie safe.
If there is no breach, a blockchain is unnecessary — it is trivial to log transactions. It is a myth that an update is not traceable. Databases do transaction logging and user management out of the box as part of their normal function. It is not “much more work”, you get this for free - along with all the performance benefits that a relational database has, and 50 years of algorithm optimization.
The work only begins to be necessary when you start talking about security breaches, ie an untrusted party gaining access to a node, or deliberate manipulation by the company itself. Then you need encryption at rest (a flag), plus a couple more measures that I listed above. But in this same case, if your blockchain is not secured by proof of work or similar, it is not any safer than the database — there is literally nothing preventing anyone from simply rewriting the chain. Sure, the blocks are signed. I can sign them too. I have the key of the node, since I am already there. I don’t have to include any of the genuine transactions. I can forge any of the transactions to the same level as I could using a normal database. Modifying it is only a minor added annoyance in comparison with an unsecured database with signed data. With blockchain safety, you get exactly what you pay for, in this case, zero.
This is why people are “mixing up” blockchain with cryptocurrency: if you expect untrusted actors to ever gain access to your blockchain, you have to introduce proof of work, which is expensive if you do it (CPU and electric power) and just as expensive when someone else does it. The other proofs of whatever don’t save you when someone untrusted has access to the infrastructure.
At the same time, for all of this, there is no relational access to the information, and you have to re-invent all the tools that you would get for free with a relational database.
So once again, what is the point?