So attempting to hit 20% IRR on such deals at present, is most likely hot air.

I am retired Air Force myself and building a passive income stream for the time after your service ended is a great approach I wish I would have known about when I was still on active duty.Last point: I suggest taking advantage of your financing benefit as a military member.

We’re moving to a new house now and will do it all over again: increased insulation, tighter building envelope, more efficient appliances, electric radiant heat in the floors (way better than forced air anyway), and passive and active solar instead of gas.

Just plan for worst case scenario 1-2 years of mediocre STR bookings and if you can survive this you’ll probably do well.You’ve already down the best research you can do- Air DNA plus just looking at the calendars of current Air Bnb listings in your desired area. 

I'm looking to do a vapor barrier to reduce any potential moisture, Insects, raydon, just better over all air quality is what I'm going for.

Alternatively, get someone to manage it as and Air BnB.   

What happens when you get a tenant that likes fresh air and leaves the windows open, but also likes the place warm and cranks the heat to 80*? 

The air base is expanding significantly. 

You should start by getting estimates from contractors to determine approximate roofing, heating/air, and what other repair costs are going to be, once you have those numbers, that'll make it much easier to make a determination if the after repair value justifies the expenditures....

Im in about the same steps of the process as you, but I will say- Air DNA is very much worth the value.