There is now a beta branch for the GunTools grip script, it aims to provide a bunch of utility for common gun interactions (including a custom late update that allows for full two handed adjustments).
It is feature incomplete currently, but the Offset hand pivot, recoil instance addition, and a few other utility items are in it already.
I will probably be moving some of the more advanced two handed grip smoothing features out of the default grip script and into the gun tools one, I doubt that most people have all that much use for them outside of guns.
Also I recently added a CustomPivotComponent to the motion controller to help people trying to do remote grips (end of laser beam ect).
The core concept is that you are providing a new component that all gripping is offset from instead of the motion controller itself, and you can enable / disable it at will. I was originally going to make it a grip script to be on a per object basis, but realized that for mobile and 3DOF VR it would be very useful to be a global setting that could just be enabled for remote gripping. The reason is useful over just using a relative transform that is far away from the controller is that it is easier to move the base point with the end of a laser beam or some other object and allows for full use of center of mass. It also means that you could enable it to just move the pivot point of the motion controller down into the palm more for all grips instead of doing it custom in the gun tools grip script.
Video going over it
