I was fairly dubious of this when I first saw it. My love for all things Fallout overrode my mild dislike for ponies. The reactions and mechanics really drew me in right off the bat. Like the actual Fallout Mod, but more indepth, with a deeper research tree and more options. Outside of the fact my combat armored security force had four legs, carried their batons in their mouths and some how had a riot shield welded to the side of their armor, I could cope with it.
But then, a horrible mixture of Radstorm and immigrant wave sealed my delight with this mod. I had some minor experience with radstorms, watched them effect local wildlife, and knew it was best to get undercover if it was coming my way. Not an option when both a storm and a migrant wave spawns roughly at the same time, in the exact same spot.
It... was horrible. Some of the migrants managed to rush through, any where only effected by minor radiation sickness and some burning. Others... Were not so fortunate. A few were covered head to hoof in blisters, and one... a fisherpony... She was rotten. She was on the fact tract to ghoulification if such a mechanic worked. I hoped, with all my heart, she died before someone could recover her. My hospital, a well stocked and fitted room, was overwhelmed in a matter of days. The free wing of the Warrens was being used to stock the overflow. Miasma was everywhere. I checked my medical pony, also the Expedition Leader. Removing rotten flesh. Performing Surgery. Cleaning Patient. She didn't even return to her quarters. She passed out in the hospital after finishing a final surgery. For all her efforts, most managed to make it out of the hospital and rejoin the Stable, joining with the security force, the ever growing mason guild, or working below the earth in the dim glow of the magma forges.
I have suffered ambushes of slavers and raiders, even a pair of sieges. All have broken against the shield of my baton wielding security force, backed up by the unerring aim of my rifle squads. Still working on gathering all the supplies to begin magical studies. It seems a luxury I can not afford while still battling the elements and hostile forces, but I know it will be required if I ever have to face Unity.
All and all, you manage to take ponies and one of my favorite settings and mesh them together nicely. Good show.
Now the bad:
Scavenging has no set skill. I tested it, and even a pony with nothing set will go off and scavenge. This is very annoying because I will suddenly find my Master armorsmith, who is deep in the belly of the earth refining all my scrape into metal, running the fifty some odd levels to refine a chunk of scrap, and then run all the way back down to resume his smithing. This happens with all professions. The other fallout mod used the near useless skill of animal trapping as it's place holder, rather try to make a new profession. It works fairly well.
Have you thought about changing salvage raws so they are unusable for carpentry, but still counted as wood? i have had a few starts where I was able to begin with some 6000+ ponybucks, because my starting wheelbarrel and such were made out of high quality salvage. This would allow people to stockpile wood in the same place, but not have to worry about their woodburners torching your disabled terminal logs because you need coal for steel.
Thoughts for items:
Taking another page from the Fallout Mod, and your own premise for the Everlasting Fountain, adding a very rare power source for a furnace or smithy would be a god send. Something stupidly rare, only in the Ministry of Wartime chests (Maybe magic) which allows you to build a forge that doesn't require fuel for basic smelting (No metallurgy reactions, like steel, bronze, etc) but allows you to smelt down scrap or work on smithing skills without having to dig down to magma, deforest the landscape, or micromanage your lumber/scrap industry quite as much.