What exactly is a coil tap?
? HUMBUCKERS can be tapped, to provide a single coil tone, sometimes the wiring for this is installed when the pup was made, often it has to be added, usually by changing to a multi-condictor cable. And then we need some way to select this feature, a switch, push-pull pot, etc. Or, if we’re clever, it can be added to the existing tone control. Probably the mods to the guitar for switching, etc, affect the value most. If we avoid new switches, etc. then it’s only the devaluation of having non-original wiring. But I sure wouldn’t do it to a vintage PAF….