So here are my thoughts.
Cuffing right now causes items to drop from the cuffee's hands. When the ling items (sword/shield) are "dropped", they revert back to normal arms. This is tested and confirmed working.
Forming an arm blade or shield causes cuffs to break. Intended and working.
The shield disappears when the ling is unconscious, but not the blade. More on this later.
So with this information, we look at the rationale presented by both sides. Mechanically, changing this or not is more or less irrelevant. Why? Because if you can be cuffed, as it is currently, you can break back out as soon as you're conscious and able to. And if it WAS changed to where you could not be cuffed, not much would change, either. After all, those cuffs you put on the ling would last only until they were conscious and felt like breaking back out. Of course you would still want to cuff them, at least for the first time, as knowing that they can break back out before they demonstrate it is metagaming.
As for the "it's cheese that you can cuff a thrashing arm" argument, I have to disagree. If you're being grabbed aggressively (prereq for cuffing), you're restrained by the person; you're no longer thrashing.
So with the mechanical difference being very minute at best, we look to the argument of "Is this silly?" And I find myself agreeing with Garn; the arms simply aren't arm-shaped anymore. Cuffs would slide off a blade, no matter how thin or thick we headcanon the weapon to be. The shield, too, presumably turns the wrist and hand into a large surface (Even the shield description indicates a pattern of fingers), so you'd realistically have to cuff further up the arm. And since we assume you need enough "arm" to swing the blade, you can probably cuff further up the arm there, too.
So the change I will be looking into implementing is more or less as presented in the suggestion: Normal cuffs, IMO, should not be able to secure a ling who has a shield or blade out. However, zipties, tape, and cable cuffs I will still allow to work, as those are more elastic and presume you are applying cuffs to the bits that you can actually reach. I will also probably change the arm blade to retract when the user goes unconscious, to make cuffing them when fully disabled by pain and damage an easier venture. If they went through the work of disabling a ling, they should be able to cuff them. And I don't have a problem with this, as cuffs are no longer a round-ender for ling. Either item or form (lesser or horror) allows you freedom.
I do not know when I will do this change or if this will be the final implementation, but this is my thought on the matter as of right now.