I like the tank barrier stuff. However, the rugged terrain (where I am speaking of) is so full of trees 3 feet thick, and boulders the size of buses and yahts, that tank travel would be impractical.
As for gas tanks, roads, etc... There is none of that stuff where I speak of. The only realistic approach would be on foot. There is no other way.
I think the kind of place you speak of could be of use elsewhere, in other communities... but when all hell breaks loose, I will not build a community where people addicted to modern contrivances are free to go. For me, it is cave man style, or nothing. I have nothing against others creating the kind of place you mention... and certainly there is a need for them, but I do not trust modernization.
If you can drive a vehicle there, it's not safe.
If you can be tracked easily, it's not safe.
If you can be detected from the air, it's not safe.
Now I would like to mention something. I know this will scare some people off, but that is too bad. While I was running my survial school, I became very discouraged about my dreams for what I wanted to accomplish with it. I won't get into my ideas, lest big brother is watching... which would identify me. So, like I said, I was discouraged because I felt everyone thought my survival stuff was fun and games, and downplay the potentiontial for my movement to sink down some roots. I never told anyone I was discouraged. However, our mid-wife who is a great intercessor and woman of God approached me and said, "ancientskills, (i omit my name) I was praying and God spoke to me. He wanted me to tell you not to be discouraged in your pursuit of wilderness survival skills, because the persecuted church is going to be so thankful that you took the time to preserve these things".
Now, I took it with a grain of salt. When someone tells me "God told me to tell you", I am wary. However, as the years have gone by... I believe this word was prophetic. I used to think it was impossible, but not any more. Persecution is at our door.
Now since I genuinely feel that this is a high calling of God on my life, I must remain true to skills, structure, organization of what I have developed. There is nothing like it. It is something I will have to introduce to people. I honestly see myself as a wilderness underground church pastor...and minuteman. So for the sake of this conviction, I can't adopt plans that allow for modern equipment, unless it can be carted in via canoe and on foot. Anything else is a give away to people who will be fleeing society to worship God freely.
But there is a place for other communities... with gas tanks, and vehicles, and water tanks, etc. I feel the underground communities could be like the church: the hand can not say to the foot, "I do not need you". Because we are one. Even so, communities have their purpose, but my high calling is for total primitivism: living like natives... but with tactical arms as well as primitive ways.