we’d all have to just trust miners.

Isn’t this a natural part of how the bitcoin protocol works? If a block was found and the miner decided to do something like accept tx containing new bitcoin after only 99 confirmations, and other miners accepted that block and kept mining on top of it, there is nothing we could do short of adding hash power to the network that rejected such behavior. My little non-mining node sitting up in AWS instance can reject it to high heaven, but it’s not going to ever mine a block on top of the last ‘valid’ block. Put up or shut up basically.

Or am misunderestimating something?