In the case of The Office of the Public Guardian v Both & Another MHLO (2013) 88(LPA) has confirmed that it is not possible to provide in Lasting Power of Attorney for more than one replacement. Where there is more than one replacement set out, then the whole Lasting Power of Attorney becomes invalid.
This does not however preclude the possibility of there being two separate documents, each with a replacement attorney. They could then be held in reserve and not registered. It has been suggested that, if before incapacity, one set of attorneys are no longer available, then the second Power of Attorney might be registered.
This solution is however fraught with difficulties if nothing is registered prior to the person losing capacity. As such, we could not recommend it without taking legal advice.