Who are some really cool super heroines that you could easily throw a cosplay together for in a week? That aren't too popular though(ie wonder woman, starfire, etc). :3
Power Girl
Ruby Rocket
Jubilee
I don't know how long it would take you though.
Oh, and I always have to suggest Harley Quinn because there can never be enough cosplayers of Harley in my opinion.
Of course! I mean Harley is like a ninja, you can never have too many!
What would be even more cool is if Harley came to MEWcon ON a Harley
Harley Quinn riding back seat to Joker on a purple Harley-Davidson.
*insert joker laugh*
Meanwhile I've got cosplay ideas coming out of the woodwork. Like Christmas themed Finland for the Hetalia shoot, and a combined MEWcon mascot for the fashion show put on by BangBangNeko, in addition to the five I have ready to wear across the three days.
But hey I built Inuyasha with the pieces I needed on my way to Kumoricon '08, and rebuilt him at Sakuracon '09. So come as something and you just might find the last few parts you need up there.