Imo I think people have this romanticized idea of what cosplay is. We’re literally just dorks in silly costumes – and I mean that very lovingly. Sometimes we’re dorks that really look like the characters we are trying to portray and sometimes we look…well, like dorks in silly costumes lol. Sometimes the costumes are well crafted, sometimes they are held together with hot glue and prayers.
If you’re worried about people judging you while cosplaying, I suggest looking through some convention photo galleries. Not a photographer’s collection of private photoshoots, just hall photos of a con from some random attendees. I found a collection from Dragon Con here. I’ll even put a couple or links to some galleries to make it easier: [x] [x] [x] [x]
Tons of different body types, different ages, wearing wigs or going without, different skill levels – just a bunch of dorks, in silly costumes, having a good time! Not only that, but that congoer with a camera thought those cosplayers were awesome enough to photograph, regardless of how well they matched to the character.
but back to the question…
Yes, I think it is perfectly acceptable to cosplay outside of your body type. Otherwise many people who do cosplay may have never have joined the hobby in the first place, and even if they did the choices would be so limiting.
Before you think about other people, what do you want to do? I am guessing you want to cosplay the character. So what is stopping you? Oh right, other people.
Do you share their concerns? Do you feel uncomfortable wearing a miniskirt? If so you can look for alternate outfits that the character might have worn, or make the skirt not-so-mini to make yourself feel more comfortable and confident in the costume. You can wear a pair of shorts underneath to avoid accidental flashing.
If it’s just their concerns, and not one you really share, then you can choose to listen or you can choose to ignore them. There are always ways to alter costumes and there are always more characters to choose from. But I definitely think there is empowerment that comes from dressing as the character you want in the way that you want, and giving it 110%.
Best of luck in whichever you choose.