Valve Cap should be renamed Dust Cap IMHO.
Primary seals are on the valve core and a core has a specific torque loading when it is fitted. If it bothers you line techs that much because you cannot ADD the cappy thing, think about putting an IOR to you quality department. They can go to the regulators and the type OEMs and see if the senario can be put in to MMEL so the operator has the option of adding it to their MEL if they see fit.
Simples.
