The issue I foresee is this: how does the retailer satisfy itself that the person it is sending the moderator to is the same as the individual on the licence? Without a person to check the likeness of the individual to the paper licence, the purpose of photo identification is lost.
That said, when items would no doubt be dispatched to the address on the firearms licence, its not likely creating a situation where components are being acquired unlawfully.
I imagine it will turn on what each RFD's licencing authorities attitude to risk is. By analogy, you can buy shotgun cartridges online; you just need to send in a copy of your licence for verification first. Perhaps a similar practice will ensue here.