allow animate Motion Blur checkbox

"you can animate everything in blender" (fields, checkboxes...)

I ran into a situation (see below) where a quick solution was to turn off motion blur for just 1-3 frames, while keeping it on for the vast majority of frames. Imagine my surprise, when I attempted to do so permanently in an animation file, by animating the checkbox for [x] Motion_Blur :

(hover over checkbox & press 'i' for insert keyframe) -->

"use_motion_blur" property cannot be animated

Situation:

• animating a character.
• toggling between Inverse-Kinematics (IK) and Forward-Kinematics between frame x and (x+1)
• I have character's parts at same locations in frames x and (x+1).
• [x] Motion Blur is on
• Rendered frames in the range (x-1) to (x+2) show blurred motion that does not exist . --> When frames are turned into video, it looks like an obvious glitch.
• Simplest fix (for this bug?): turn off [ ] Motion_Blur and re-render just 1-3 frames. --> When turned into a video again, with motion blur off for 1-3 frames, there is no visible glitch.
• For 1-time patching, it's ok to do this manually... but I'm working on an extended animation, and I keep re-rendering the video to test small tweaks & timing... so I thought to just animate the "use_motion_blur" property to get this fixed automatically in each re-render.
• "use_motion_blur" property cannot be animated

It's not just the IK/FK toggle that manifests motion_blur glitches: I also get this at the ends of NLA tracks if I do not have extended fade-in/fade-out 's. --> If an NLA track is shadowing a lower track, & has fade-out=0 (zero) frames, but there is no motion between frames 'end' and 'end + 1' , then Motion_Blur creates blurs for motion that doesn't exist: visible glitch.