I'm pretty new to managing ponds so my reply will not be so much as advice but more ideas that others with more experience can expand on.
If it were me and I had to be the one to eat the fish, BG and LMB with a few RES for grub control would be my choice. CC produce well in small ponds but from a sustainable preppers standpoint the issues already mentioned are valid. Since the assumption is "future emergency food" and not "current regular consumption food" I would also leave the CC out. BH would be a self reproducing catfish and are easy to catch, and might be a better choice for catfish from a preppers standpoint, but I also would not use them.
Although I am fairly new to managing ponds, as a farmer I have been around small farm ponds since I was a kid and have witnessed people fishing them for many years. The standard fare for farm ponds in this area are LMB and GSF. Not the most desirable fish from most anglers standpoint, but they survive with absolutely no management whatsoever and just about any pond you can find around here will have those two fish in them even if the pond has not seen human intervention for years. A fair chance there will also be BH.
One other fish that might be worth consideration strictly from a survival standpoint might be common carp. Everybody will immediately turn up their nose to that idea, but carp were as I understand it originally established in this country from Asia as a potential commercial food fish. Carp, although not an anglers choice or most peoples food preference fish, are a good source of protein and if pressure cooked are very much like canned tuna as far as eating them. My wife has prepared them that way back when we used to spear fish carp in local lakes as part of a scuba/skin diving spearfishing competition event. I think they are very much used as food in a lot of places other than the USA. They are definitely a source of protein that are easy to raise. What I am unsure of is how they might interact with other fish in the pond from a long term sustainability standpoint. The experts would need to weigh in on that issue. But carp can utilize sources of low protein food (like field corn, table scraps, etc) and turn it into protein better than game fish like BG and LMB. So carp might be a consideration from a preppers standpoint.
Something also worthy of consideration is how you are going to harvest these fish should you need to. The obvious first thought is hook and line, but in reality from a preppers standpoint and survival, something like fish traps or a seine may more fit into what a person might actually do if a person was dependent on these fish for food in a self sustaining survival situation. Then angling ease of catching the fish might not be much of an issue. The pond design or your proposed method of catching the fish might be more important. I have heard an old hand crank generator out of an antique telephone with two wires in the water will work, but that is just what the big boys tell me.......... no personal experience that I will admit to. I will say such a device will get a person kicked off the school bus when implemented in having a bunch of kids holding hands while cranking it.......... and one of the little sissies cries......... don't ask me how I know.
