If I can avoid Double NATing, I do because it tends to degrade network performance and can have interesting characteristics on some inbound traffic (although that depends on the use case).

But the third option honestly isn’t recommended enough. DoD space is rarely routable, and if you are on a private network already, even moreso. It’s also less common than RFC1918.

However, there is one caveat. Some large corporates do use it for just the same reason. Even though it is rarer than 10 or 172 space, you’d be surprised how many large orgs do run DoD internally.

(Disclaimer: I use DoD space for my travel router at hotels)