> Maybe we want code like this

It should be clear enough that this operator isn't going to run 'new' on your behalf. For layers you want to leave missing, use "?.". For layers you want to construct, use "??=".

> Why would you ever write an assignment, but not expect that it "sticks"? Assignments are pretty important.

If you start with the assignment, then it's important and you want it to go somewhere.

If you start with the variable, then if that variable doesn't have a home you don't need to assign it anything.

So whether you want to skip it depends on the situation.

> What if someone doesn't notice the question marks and proceeds to read the rest of the code thinking that the assignment always takes effect? Is that still readable?

Do you have the same objection with the existing null-conditional operators? Looking at the operators is important and I don't think this makes the "I didn't notice that operator" problem worse in a significant way.