Most elegant solution would of course be to complete the eyewear slot on infected and give it the same functionality with headtorches as the headgear slot has currently. This would also allow the already prepared infected glasses arrays in random presets to be used.
In the meantime I made a mod that lets the headtorch go into both the eye and headwear slot, not as elegant since players can then wear two headtorches simultaneously if they want. Not a major issue, but still...