Would have said exactly this had i seen this any time in the past 8 years:
Avarage = HORRIBLE idea.
One has to be the leader, the other has to be the follower.
Nothing prevents you from coding up a switch between who leads and who follows to create some interesting gameplay effects…
Ps:
Nice demo.
You should add some lerps and refinement between holding/not holding.
You can easily clean it up by using the newer animation recording features that let you record and scrub through what happened and where.
But essentially, if you just lerp the Ik alpha over 4 to 5 frames you will just never notice any glitch like behaviour…