The first thing I thought when I saw the Outerra engine was "this is how Arma 3 should have looked like". Infact the engine gave me a very Operation Flashpoint-esque feel, with it's military vehicles, aircraft (Cessna, Apache), trees, ground textures, a "clean", realistic look, massive worlds, ect. Don't missunderstand me, I'm a fan of the Arma series (OFP in particular) and it's "Real Virtuality" engine (which may have some issues like poor multi-threading support and other things, but it's incredibly flexible, moddable and upgradable), however sound competition is always a good thing, especially considering the state of things in the realism-focused military shooter/sim genre.
So my opinion is that the Outerra engine should deff. be considered for making a massive military type game focused on realism. Picture a kind of "virtual war" scenario that would take place across the whole globe, in areas modeled after the real locations and a persistent, ever-changing online world, where new content would be added by a highly moddable engine but also via official DLC content by the makers, where the core game would be free but the said expansions would keep the project going, where you would choose your fraction or nation for which you would fight for, where international borders would be written anew, where armed resistance to existing regimes would arise, where there would be a kind of "strategic map" where you could choose strategic options and combat engagement and view the global situations unfold, where servers could host thousands of players at once, where one could choose to be a mercenary for a certain fraction or nation, where there would be tons of different military vehicles and weapons to choose from, ect.
Kinda like what World War II Online is but with the Outerra engine and all it's advantages and a present-day scenario. Imagine fighting an imaginary war in the Crimea region, in Syria, in Sudan, ect., where every world nation and conflict locations would be appropriately represented. It would take the term "Virtual War" to a whole new level, especially if one would consider full compatibility with the emerging VR devices like the Oculus Rift and Cyberith Virtualizer.