default crop

 Part of the new crop logic is there is always a crop.  IOW, there is no longer have the concept of "no crop", just a "wide open crops" (full frame, full image so to speak).  So the state where the crop is locked to some specific aspect ratio but the image is still not cropped no longer exists.
 
There's a number of ways to save the crop, depending on what you want. You can do a "Copy Settings" and then "Paste Settings: if you have a number of images selected. This can be done from the filmstrip clicking on the three little dots.
You can also do a "Save Settings" as a Preset and call it up at any time using a similar GUI. If you only wanted the Crop, you'd probably select first "None" then just click on the "Crop" check box, give the preset a name then recall it whenever you wanted it. You can even save this out as XMP to load but a preset is probably better (XMP would be useful for saving across multiple computers). 
 
With the Preset, you could have just this crop but you could have a crop and any of the other settings built there too as seen below where I have crop and geometry in one preset. 
 
You could probably save the crop as a new raw default but I don't think I'd go that route. I'd prefer to start without a crop which is how it now works, then paste or set a preset depending on the need, edit that from there if necessary. But that should allow a 'default' though out all photo's.