I just assembled an AR without buffer and buffer spring. Doesn't take much of bump to open the action.
The Specter bolt action bolt carrier is lighter, but a bump could still start the carrier moving backwards, either creating an opportunity for a misfire, or even opening the bolt.
A simple nylon detent plunger would prevent this. Perhaps located where the bolt hold open would be, it could engage a notch in the carrier, or even the rear of the carrier. First pressure on the bolt handle would override the detent, and drag on the carrier while the action is being cycled would be minimal.
I think that the idea is an excellent one, ban or not. Lots of AR parts with which to assemble a handy modular rifle.