Well, that's a shame 
I do know many other people are hoping the do expression proposal goes a different direction (as I've linked in to in my O.P.), so I'll try to keep pursuing this idea and see where it leads.
On another note, I was remembering this "catch pipeline operator" proposal recently. It's intended to be a follow-on proposal to the pipeline operator that provides catch-handling semantics. i.e. if the pipeline operator is a sync version of promise.then(), then this proposed operator is a sync version of promise.catch().
Example:
const result = getId()
|> getUser(#)
|^ # instanceof NotFoundError ? null : throw #
|> getGroups(#)
In the above example, the "|^" operator will catch any errors on the left-hand side and pass that error to the right-hand side. It'll follow whatever syntax the pipeline operator follows (F# - where the right-hand side expects a function, or hack-style, where the right-hand side is an expression with sigils (#) that are replaced with the LHS's value).
I really love this proposal, and hope it goes in. If it does, then the only remaining thing that we would need is the ability to create declarations in an expression position.