I'm not entirely sure, it seems as though Quark's costumes were often a much more formal appearance with several layers, whereas Neelix's costumes seem more colorful but simple with just decorated pants and a coat or tunic.
Hey all,
My theory is IF they do a Neelix, they'll put him in a security uniform the same way they did with Kira in FC uniform. I'll still be happy if they do.
Take care,
Matty-lad