But you're overlooking something though, the Enclave has no use for tanks, the USAF wasn't the Enclave, they were unaware of the Enclave's existence (well, the grunts and average troops). A good 80% of military hardware available Pre-War is quaintessentially obsolete to the Enclave. They have Vertibirds, Adv PA Mkll, and a varying degree of high end tech. Also take into account looters, and those bases are worthless after being plundered for over 200 years. As to farmland, don't forget, we aren't sure how fertile it's land is after the bombs fell on the United States, so it's hard to say. Honestly, there are to many unknown variables at play here.
I would imagine many military bases, enclave bases, have mad insane security systems to get into.
Would be fun to actually explore a Poseidon military reasearch center. Who do we send? Enclave private Gary, of course.
After getting past security robots and turrets, Gary is faced with Zax computer asking for password in.
Dialog options:
1. Science 100 ycfgy36-gh960
2. Speech 100 set poseidon overide delta gamma bravo
3. Gary?
4. I don't know.
Option 3 selected.
Zax computer confused and asks again.
Dialog option : Gaaaaary. Gary!
Access granted.