I hate your suggestion. "Defaults" inevitably seem to get used to push some thing I don't want - for example "open in google docs". I don't want another click added so I have to navigate away from whatever cloud storage is being shilled by my browser.

I think the answer is that some of the browsers actually care about how their users use them and don't want to add extra clicks.

That said, being able to specify a default location seems fine. I thought I could already do this in firefox, so of you want to, just setup the default so it saves to your cloud provider