State Consistency by Filecoin

[Yu-da-1]

Hi, I am developing a Decentralized Personal Data Store (PDS) called Monas.
About Monas: Monas: Privacy, Data Interoperability, and Self-Sovereignty in Decentralized Personal Data Store v1.0
We recently developed a prototype at a hackathon organized by Protocol labs. To briefly describe Monas, it builds a cryptographic data structure called Cryptree, which allows users to intuitively and flexibly control access to the space.
Github: About Prototype

Main question

Monas stores operations such as directory and file additions and deletions on Filecoin for PDS consistency. I believe the use of blockchain for state management is optimal.　One thing to note here is that consistency is not a state of the data, but a state of the PDS space. Data is currently encrypted and stored on IPFS. This means that a CID is generated, so it is easy to check if the data has been tampered with. We are also developing a write function, which will allow us to prove who wrote the data by signature it. What we want to prove is that the current PDS is up-to-date and has not been forked (tampered with) .
Blockchain is a great solution to this problem, but as you know, every time an operation is performed, a transaction is executed. This means that each time an operation is performed, gas costs more, and performing the operation is more expensive than existing services. Sure it is great that users can manage their data in a self-sovereign way, but if it costs more money than existing mechanisms, it will not be used.

So I would like to know if there are any approaches to this problem or related studies.

Currently what I see as a possibility is to form a Merkle tree or DAGs locally and make it manageable on the network.　I do not believe that PDS, for example, requires as much consensus as blockchain because it does not involve a transfer of value.
So I think it would be better for users to select some nodes (of course there would be a minimum threshold) and form a network.　Here, the relationship between the blockchain and this network is such that the blockchain is the endpoint and the network can be discovered by someone exploring the state of the PDS. (Of course, this is a problem if the nodes can be identified, so some method is needed.)
How to actually form the graph of states on the local, how to build the network, etc. are still in the conceptual stage, but if you have any opinions or thoughts, please let me know.