Interesting. I put "middle man" in quotes because I can see it wouldn't have to be a person or group of people. I can see imagine it being a protocol. 

kepford

I totally agree that reversible transactions have tradeoffs, I mean they cause all kinds of fraud, and costs the banking / financial system much more to deal with.

Rock

bitcoin

Does Bitcoin have any negative tradeoffs or is it just all positive?

So I have some experience with protocol level escrow stuff, like in lightning channels or even in Bisq, so I think there might be a way to do it without a 3rd party, but regardless adding that middle-man or escrow protocol adds additional complexity and time to complete a transaction. Just throwing out my thoughts.