This is a great idea and very straightforward, too.
But I'm wondering are the issues about a clear written contract or are they about fulfilling that contract? Possibly, it's both. This helps to solve one part of the problem and it certainly deals with the he says, she says problem because anyone can go and see it for themselves.
I find myself in everyday non-blockchain life that no matter how clear the agreement and how much time has been spent negotiating it ... people still don't do their bit, forget/dispute what their bit is and generally behave as if the (written, signed, argued over for many meetings) agreement doesn't exist (silent scream).

Even with a contract in place, if someone is a no show, there's still going to have to be legal action for recompense or recovery. I'm wondering what standing these contracts would have ... has anyone tried yet?

I agree with you about professionalisation, though - it's a process for all parties to learn how to manage risk and what research to carry out about another party's reputation/activities.