I see a few issues with making the Muv-Luv Trilogy into an anime :
First, just like a few said before me : the length. Alternative may be the best visual novel ever made, but it can only claim this title if it comes with Extra and Unlimited. And since the whole series, with each game put back to back, is incredibly long, it's gonna be really hard to fit everything into an anime. @Reavan mentionned a format like Hunter x Hunter (which is, basically, doing everything faithfully no matter how long it takes), which would work, in theory. The problem here is the demography : HxH is a very popular shounen anime, with a broad demographic so it's not as hard to gvet the fundings for a long anime as a more obscure title as Muv-Luv, aimed mostly towards late teens and adults, meaning a smaller demographic, and by extension less possible fundings.
A good example is Fate/Stay Night : A very popular franchise thanks to the anime adaptations of the fate route (now matter of how much of a massacre it is, most people don't know the VN exists at all) and the Fate/Zero LN, with the Fate and UBW routes having deep shounen roots. But the anime version of each route took two seasons just by itself (with UBW cheating by having a 1-hour prologue and a few 1-hour long episodes), and the Heaven's Feel adaptation is gonna take multiple movies, even with several scene cuts.
Now back tu Muv-Luv, which as a trilogy is definitely bigger than F/SN. There's no way to make it into a 2-season anime with cutting some big plot points. The only place where you could really save space are Extra (you need enough time to emotionally connect to the main cast. Probably not a whole season, but definitely not just a few episodes) and the very beginning of Alternative (which is close enough to Unlimited to be sped up). But that's definitely not enough.
Second, there's the content. As said above, even by 2003 standards Extra was cliché, nowadays it's even more ridiculous. With the general "4-episodes rule" (watching up to episode 4 to see if an anime is worth watching or just be dropped. not a real rule and more of an advice) most people won't go further because they don't know what's (far) ahead, and even if they knew either they wouldn't bother watching everything and just skips to the good parts of unlimited or straight to Alternative... which kinda defeats the point of the whole franchise, and that's if they don't just entirely drop it.
Aslo, thanks to Total Eclipse and now Schwarzesmarken being released before Muv-Luv trilogy, people would just assume it's yet another spinoff because it's coming after both of them, it's not well-paced at all and searching stuff on google is haaaaard ( quite a few people not even aware that Schwarzesmarken isn't a standalone anime, but part of a franchise ).
tl;dr IMO Muv-Luv anime would a bad idea because you can't fit the whole stuff in an anime and most people wouldn't bother watching up to Alternative anyway,