As I understand, the ‘edit’ pop up window in the ‘shutter curve’ within the motion blur rollout allows you to set the motion blur from 0 to 1, which would be the equivalent of fully closed and fully open.
What if…we can set that value to 5 for example, to allow for a very exaggerated motion blur, while keeping DOF at a normal level?
Motion blur has nothing to do with depth of field. If you need more pronounced MB, just make shutter speed slower, this will not affect DOF in any way.
You can’t get more open than fully open 
And yes, just change the strength of the motion blur via shutter speed as then “1” will show even more blurring, just as you are looking for.
Got it. Sorry. It was a dumb suggestion.
I meant to say it would affect brightness, but I use simple exposure anyway.
Shutter speed in photographic parameters works perfectly.
Thanks!