These are smaller issues, but here are three non-personality arguments for why there shouldn't be so many chainmail bikinis:
1) Not everyone's into that. When I said earlier that I find a women in practical full plate more attractive than a plate thong and bra, I meant in a physical sense. Gimme a bit of sweat and grime, and some flesh on those bones, arms that look like they could actually lift a broadsword, and you give me one of those awkward boners. You want women with super boobs in a two piece? Fine, but I want girls that look like they could kick my ass. More variety = more varied appeal.
2) Remember that female characters are often role models, intentional or not. If all girls see is these incredibly (and stereotypically) sexy women, they're going to have unreasonable expectations for their own appearance. Physical appearance is a big deal for women (generally speaking), so this sort of stuff contributes to body shame. This is a not-insignificant contributer to anorexia, bulimia, and depression. Barbie got a redesign for this very reason.
3) This is only a problem for things that require live actors (so very rarely something that has to do with video games), but the vast, vast majority of female acting roles are expected to be physically attractive. This isn't true for males; you can find plenty of movies with men that aren't stereotypical hunks, but it's rare to find a moderately unattractive (but not hideous) female character. This is an employment issue. Talented actors are being passed up because they don't have the right hourglass shaped body.
Fact is, being physically attractive is way, way overrated for female characters and it's having quite a few adverse effects.
Re: JRPG and anime female characters.
Japan has its own gender roles and stereotypes. They just seem better to us since they're not acting like western gender stereotypes. They're typecast into "female" roles just as bad if not worse. For example, you'll be hard pressed to find significant female characters that aren't either incredibly loud (genki girls, super assertive girls, tsunderes, etc) or incredibly quiet. It's like there's no middle ground. Usually if you have a female character leading a group of some sort, they'll constantly let the people there (and the audience) know that despite being a woman, they're in charge. And they'll do this loudly. Or, you'll have a female character so quiet that it unnerves everyone and the implication is they're in charge and don't need to say anything at all. The only exceptions to this rule I've found are characters that are old (christmas cakes, etc) or occasionally some characters in all-girl ensembles.
The problem concerning female characterization is and always has been lack of variety. "Female" becomes an overarching character type, and not just one of many traits like it should be. None of the common female character types are really inherently bad; just their ubiquity.