IMHO, they should diversify - spread things out to different parts of the country. But hey... the political folks like BIG plants...
I think in true govt fashion there is terrible redundancy and massive single points of failure happily coexisting. Things are very spread out. This is also an elephant that can never be eaten, way to big. Someone in the family does material condition assessments on gov't facilities including lots of ammunition igloos. The Army is spending millions just for a company to tell them what equipment they have in what buildings and how soon it needs fixed. They have no idea.
Some stuff is too complex to diversify much. I used to live next door to they only place in the world servicing nuclear carriers. Yeah, a target. This week been building handrails for a gov't contractor, had no idea 90% of the free world's explosives gets made in Kingsport Tennessee.
Then there is inertia. I saw an auction just a few years ago where Hawthorne disposed of the remaining 16" naval gun tubes. Pretty sure in Iraq and Kosovo we were dropping all the best bombs the 1960s had to offer. Just so much stuff. I worked for a month at Bluegrass Army depot, supposedly they were still blowing up chemical weapons from pre WW2.