If you want my hoinest opinion, I believe that you doesn't appreciate it overall because you were so wishing to get your design (of course, nothing wrong with it).
Even if maybe not the most original design, I believe that it's perfect for showing the girl mainly (in a tomboy way) and sexy at the same time, the perfect mix for representing Mila in the series remaining loyal to her personality and at the same time going toward the fanservice fans.
While I'm not gonna lie I'm disappointed I lost, I went in knowing I wasn't going to. Its just that this costume honestly was one of the ones I REALLY DIDN'T LIKE, from the very beginning. If they were going to use a military outfit, they should have gone with one of the other two, not this one, that obviously won simply because the art was "cute".
Anyway I agree with you that the trend followed for the fan design was already overused in the game for other outfits for Mila, however here is the fault of TN not of the fan that designed it (especially because the cop one, for example, was surely planned later the decision to create the fan design for LR).
You're right, I was forgetting that there were even other variations of the military uniform. By te way I'm not sure if they really chose it for the cute art, look for example to Kokoro's desing, definitely they didn't chose the design where Kokoro appeared better looking.