I am currently in the military as well and have bought quite a few homes using both conventional and VA loans.  

I'm interested rehabbing a property and refinancing the hard money it into a non owner occupy conventional loan of 75 - 80 percent of the ARV.

For conventional financing, it does.

I'm considering a property for rehab in southern NH that is accessible by a class 6 road. I'm concerned that this will be a problem for my prospective buyers post-rehab when they try to obtain financing. Does anyone h...

There would be absolutely no 90 day seasoning requirement for conventional loans, cash buyers, or transactions with seller financing. 

I made an FHA loan offer for $305k (right now I have enough saved up for an FHA loan, I might be able to do conventional also).

I have been studying the markets around me for months and have been putting in offers regularly and have yet to get one accepted just simply because of how hot the market is right now and the very low levels of inventory available. 

With option 1, you'll only have 1 paid off property in 30 years when you need the income (assuming you do a conventional 30 year mortgage).

But searching through listings available online, there seem to be quite a bit of inventory as well.

But some circumstances require that the property be held, such as when the end buyer is getting a conventional loan and Fannie/Freddie requires that the loan app be dated AFTER the B Buyer close on the property and officially is the owner of record.