This can already be effectively done, though. I don’t see why the default needs to change for everyone. I appreciate your working style—I interleave a lot of notation into my Draft folder as well (though nowhere near 75%). So I get where you’re coming from—but if you do have that many note documents in your Draft, perhaps you should set your Draft up to use a notation document by default, instead of a default text document. This is pretty easy to do, and if that is what you always want, go ahead and set this up in a blank project, save it as a starter project template for yourself, and use the “Options” button in the New Project window to set it as your default. Now Scrivener works for you instead of against you. 
I’ve attached an example project template that demonstrates one approach. For it, I just created a “Templates” folder, used the [b]Project/Set Selection as Templates Folder[/b] menu command to give it the special icon and work as document templates.
Within that I created two new documents. The first one in the folder is special, it will get an alternate keyboard shortcut added to it so that it is easier to create. I’m going to be setting the “Note” type as default for Draft, so you want a way to make a actual printable draft document easily, too. This is just a stock file with “Include in Compile” checked. The “Note” document has a special icon and has “Include in Compile” disabled.
Finally, I select the Draft folder and use the [b]Documents/Default New Subdocument Type[/b] sub-menu to select “Note” as the default type. Anywhere else in the binder, I’ll get an ordinary text file, but in Draft I’ll get “Note” instead.
As mentioned, to get an actual normal file in the Draft from now on, you’ll have to use the [b]Project/New From Template/[/b] sub-menu, or the [b]Shift-Opt-Cmd-N[/b] shortcut to add one with the keyboard. All normal ways of adding a new file to the Draft (and subfolders) will result in a “Note” file otherwise.
That probably all makes less sense than just trying it out for yourself and see how it works. You should see that the “natural” ways of creating new content in the Draft folder are result in yellow-icon Note files, that’s your 75%. For the rest, use the shortcut or sub-menu as described.
Notes.scrivtemplate.zip (42.8 KB)