the biggest point of failure on some nikon lenses is the 4 tiny screws that hold the foot base on the lens itself coming loose .
one day i felt my 2 week old nikon 600mm pf f6.3 moving slightly on my monopod .
a further check showed the 4 screws were loose .
a quick check on line showed it’s a common problem on some nikon telephoto lenses .
so far some loctite has prevented them from loosening up again .
but that to me seems the weakest point for failure but i see no way of tethering a nikon lens itself and not from the foot
I really don't know if that is the case, however, my 800 PF arrived with the foot seemingly intact and yet two of the four screws were loose. One was significantly loose, while the other one was only slightly loose; this was determined when I swapped out the foot for a Hejar one. If I remember correctly, the screws had some form of white thread lock (?) on them and yet they arrived this way. Was it a quality control issue, a problem which developed in transport, or simply poor design, is anyone's guess. Having checked the foot periodically, I have not experienced any further loosening.
From the standpoint of fixation, no matter what method is employed, there will always be potential failure points. Personally, I have solid experience with QD connects with firearms of similar weights compared to the camera/lens combinations. Of note, I have never used leashes/tethers or other backups with firearms and have not experienced any failures including single point sling carry. Nonetheless, with my cameras/lenses, I do employ a safety tether though it is attached to the lens rather than the body itself. If the primary QD fails (at the foot or the connection itself) a tether to the body lug would likely be ineffective and an attachment to the camera baseplate socket could possibly cause significant damage to the body itself.
There are several ways to mitigate this though all of them are potential failure points as well. First, I performed some ad hoc testing with a small rig cage which has a built in QD on its baseplate (the cage's primary attachment is at the screw baseplate, though it hugs the camera around the body). Using the cage as the secondary attachment point, I disconnected the primary QD on the lens's foot and allowed the rig to drop - expensive and potentially perilous experiment, no? - anyhow, no damage was sustained, and I speculate that the cage distributed some of the forces around the body. Would the result be similar without the rig and against the primary screw connect? Perhaps, though I leave it to you to determine the outcome with your cameras.
If the lens has an anchor lug on it, that's an excellent target for a safety strap. In its absence, another alternative is to use a strap tether which surrounds the lens itself. Optech used to sell such a loop, though I see that it is no longer available on its website. I use a safety tether strap which has a large loop on one end which I fit around the lens and the other end connects to the strap. Admittedly, it is not a perfect solution and even with this system failure could occur.