B757: 1st command. The company was young and small and so was the training dept. I had come from a B732 and an airline with a good training dept. Thus manual no FD flying was the norm for many visual approaches. The old-school TRE on my command course considered it normal competency to fly an ILS on SBY instruments. The failure could happen and you should be able to do it. If you know pitch/power it's not difficult. In the sim session we had a sim glitch of the RMI failing, so the ILS was flown using the basic P1 compass. The F/O was very surprised it was not a major drama. Now, on B738 with a total loss of AC the captain's PFD & Map are still glowing. These are the SBY instruments, just minus the FD's. I believe this might be customer option? However, if the batteries are not up to scratch you could end up on the dark side, and a torch and tiny SBY's might be your only hope. Could you do it? Have you ever tried? Should you be able? IMHO the answer to the last is YES. The a/c is flying; there should be no reason not to keep it doing so. Sadly, because the technocrats have tried to design out the all possibilities of pilots ending up deep in the poo, training dept's and CAA's have diluted the training competency with the claim that "it'll never happen." In the world of TEM perhaps they are correct. Mother nature, human nature and mechanical gremlins will still try and line up the holes. However, the philosophy is that ever time the pilot screws up another set of restrictive SOP's is wheeled out; the a/c designers include more back-ups and fail-safe auto systems and the pilot is told not to do this or that.
It will not be long before the single pilot and the dog becomes true. That can only happen if we're allowed to take the dog food through security as all crew members have to bring their own chow these days.