It would be a bit complicated, but you could create a collection and make new virtual copies, setting the copy name to the client's naming convention. Unfortunately there's no way to batch this. You can rename files on export so the client will get the names they want, but your files won't have that name unless you add it to the metadata somewhere. They'll be talking about XYZ-001 and you'll be wondering to which file they're referring.
Mike.
Okay, this would work. Select the images, create a standard collection, and check the boxes to include selection and to make new virtual copies. Go to the Collection, select all, and go to File/Rename to rename the VCs with your client's naming schedule. Now you have two copies of each image, one with your name and one with theirs. The images will automatically be stacked with each other in the folder(s) - master and VC. If you're in the collection (not the folder) and you need to find one image (using their name) you can easily do so, and if you need to find the master file for that image you can go to the right panel for the VC, go to the metadata panel, and beside Copy Name click the little arrow. It'll take you to the master file.