Custom Upload/Picture/Cropper upload path

Is your feature request related to a problem? Please describe.
I'm using a Picture field in one of my layouts and I'm pretty happy with the functionality it provides, but there is one thing I don't like about it: it puts uploaded files under automatically created subdirectories. The project I'm working on has a strictly defined structure of folders for files being uploaded and such behaviour just makes things unnecessarily harder. It would be very convenient to have a control over such things.

Describe the solution you'd like
A path() method which allows to specify a particular path on the disk I'm uploading files to. A very similar proposal was in #1106 (here to be more precise), but it got never released since then.

Describe alternatives you've considered
It is, of course, possible to define a custom Generator class in the platform's config. But it looks more like a hack in this case, because it doesn't really add new functionality but tries to fix existing instead.