Dawn by Linsner is a fantastic curvy comic character there are many many images of her with various costumes (not all of them revealing)- you just have to google dawn costume to see the many versions.
Dawn - Lucifer's Halo Issue #2
I heartily agree with you on this, Sakara. Dawn is one of my absolute favorite female comic characters. Having been close friends/partner-in-performance/stagehand with/for a former Dawn Look-A-Like contestant (I say former, for DragonCon isn't having the contest this year, and mysteriously, Joseph Linsner apparently isn't showing up to D*Con), I have seen many, many Dawns from backstage, and indeed assisted with several myself. While I have seen plenty of "fit" Dawns, most of my favorite have been the "real women" portraying the Goddess of Birth and Rebirth. Fuller figures and somewhat "thick" does indeed fit the image of Dawn and I too celebrate a proper portrayal of Dawn.
Now, with my mind on characters that bigger women could play, in reality, any character could possibly be played. Better fit characters could be Pella of Clan Breem (from the webcomic Looking for Group,
Looking For Group) is very good. She's a dwarf who knows battle, metalsmithing, and music (she's skilled at being a bard).
A female Tron Verse character (classic or Legacy) would be wonderful too, as you don't have to portray a named character, but could make your own. I, myself, created my own security program, with symbols linking me to numerous characters including Tron, himself.
A young Amy Wong (the Chinese Martian physicist employee of Planet Express in the show Futurama) would be wonderful for the more-than-stocky person. If you are a fan (I know I am), then you know that even up to her early years with PlanEx (see the episode Future Stock for the reference I just made) Amy was a very overweight gal.
Aside from the overweight characters, if you want to be a character, then dress as that character. If it feels good to be them, then do it. You don't always have to dress as a character who shares a similar figure. Look at Tron Guy for goodness sake!
Good luck with everything, and I hope you find something that you enjoy dressing as.
Slainte mhaiph saoil fada is bas in Eireann! (Good health, long life, and may you die in Ireland!)