With SOME drives it is possible to switch off specific heads, image using the working heads, then do a head swap and image the missing 'stripe'. This can be good especially when small files (photos, etc) are required. If the new heads replicate the problem, at least you will have some data to present to your customer.
It is also possible to recover drives with corrupt p-lists which can be done manually or automatically where you can build a virtual translator based on the shifts found.
You can repair firmware on most modern hard disks, not all, but they constantly upgrade. The manuals fully describe how to do this for each manufacture and model range. If there are specific problems, they have experts in IBM, Seagate, Maxtor, Quantum, Hitachi and Samsung hard drives working at Acelab and they try very hard to find a solution.