I hope that I'll have room to make this cosplay as well, Vanille is really cute. I agree with you Enny, the beading is what looks like a lot of fun. I haven't been able to tell clearly what the front of the skirt looks like either but here are some screens that show it a little better:
It almost looks like a "loincloth" at the middle and that there are layers of ruffley fabric at the sides, although it's hard to tell. Yeah I would definitely wait because Square is releasing Advent Children on Blu-ray with a FFXIII game demo, in Japan only. Unfortunately I don't think it comes out until April but I'm sure that several new screens will pop up on the internet afterwards, hopefully some of them will be of Vanille.