I liked the pitch, as pitched, because it was clean. It would serve a similar purpose as https://forums.swift.org/t/lets-fix-if-let-syntax/. We've already got wordy syntax to do this. It doesn't solve new problems. The benefit is in the feature seeming like it's thinking what you're thinking, removing indirection.
Having to specify key paths and new variable names, as Becca and John have suggested, makes me not like the pitch nearly as much. It's a good option, but not a good default. Realistically, you're not going to need to rename things often. The names you pick will match whatever is after the last dot in the keypath. The idea is that you're digging in to a deeper indirected scope, and pulling out to the local scope, not fully remapping.
e.g. We want this, almost always…
convenience computer let (.name, .cpu.numberOfCores)
…not this, always:
convenience computer (let name: .name, let numberOfCores: .cpu.numberOfCores)
I don't encounter tuples like the following often, but you do need the remapping/renaming feature for them because index numbers can't be used as variables names.
let tuple = ("🐸", dog: "🐶", log: "🪵")
convenience tuple (var frog: .0, let .log)