I know this sounds odd, but can Ethereum be used without contracts?
This seems counter-intuitive, but here is my scenario: Groups where participation is permissionless, but all peers are governed with existing contracts, and have verified identity (IE: telecom companies physically peering with each other).
In the telecom case, imagine route broadcasts. Each network has the networks they peer with - but they don't control who are peers of the peers. So the updates are permissionless, but not trustless.
There are projects like Hyperledger - but AFAIK Hyperledger cannot handle the unknown peers of peers scenario. There is also distributed hash tables, but they are not as secure on their own.
I wrote a journal paper on this idea, but I still get a lot of pushback on this type of use. Are there any gotchas that I miss? Can Ethereum be used in this format? If interested, the journal article is here, but only tangentially related to the original question: https://www.mdpi.com/1424-8220/20/18/5281