I understand and accept (and even enjoy, to a degree) that sex appeal is a significant part of this show. It's true that such sex appeal was there even in the very first episode, given the design of those skin-tight plug-suits.
Depending on how you execute it, sex appeal can work in almost any anime show. I don't have a problem with the sex appeal, per se.
But while some ways of doing sex appeal don't degrade characters, there are other ways that
can make characters seem somewhat cheapened, imo.
The sad thing is that, in my opinion, Muv-Luv had actually been doing
a really good job of having sex appeal without cheapening its female characters...until
this episode. That's partly why I found the final scene of this episode so very disappointing, because Muv-Luv had consistently shown the skill necessary to pull off sex appeal in a much better way than this.
Having Yui walk around in a sleek, one-piece blue swimsuit for a full episode is no big deal. Same thing with what Cryska wore on the deserted island. It fits the setting, and if the male characters don't act obnoxious over it, you simply have a nice visual. A couple slightly lingering panning shots, and the fanservice is there for those that want it, while it remains subtle enough that it doesn't bother those that aren't particularly interested in it. It's win-win.
But the final scene of this episode is delivered with all the subtlety of a sledgehammer, polarizing viewers in a way that simply isn't necessary. Given the premise and setting of this anime, it truly does seem horribly out of place to me.
Now, if there was a fashion show exhibit that was planned for this beach getaway right from the start, I had honestly forgotten that. But I don't take full blame for that because Mr. Duke Nukem there acted as though Yui had to show off herself as "punishment" for getting shipwrecked... which is just absurd.
Also, why would you need such a pretext if you already had a fashion show exhibit planned from the start?
Anyway, I'm going to try to forget this episode, and if the anime starts going in a good direction starting next episode, I should be able to. Yui's character can still recover from this, but I really hope that she doesn't become
this over-the-top of a tsundere on a lasting basis.