ban-one
Works for panties
Lingerie inspired by transformers wouldn't be too difficult, but it all depends on the particular transformer. For the one you're pointing out, I'd have to buy blue boots and a blue sports bra, as I have neither, and boots aren't cheap.
And actually, if you google "sexy transformers costumes", you'll find that there are actually a few for women, but most of them are of Bumblebee. Even for those, I wouldn't want to spend the money on it. I'd never use or wear it again.
So all in all, doing costumes is something that I'm much more likely to decline for requests since it requires a decent bit of money. Doing other things that I'd need to buy stuff for, like whipped cream, donuts, etc. isn't as big a deal since those are usually between $1 and $3. As I mentioned in my OP, I'm happy to do any request (it's fun and I enjoy doing it) so long as it's within my means, and money is one of those means.
Well, the reason I suggested you possibly doing that Arcee was because to me it looked like what she was 'wearing' was things that actually existed (or close anyway), and that you could possibly already own, making it an easier thing to do. But since you don't, I understand your not wanting to buy things for just a few pictures, and that's fine