The problem is they probably want to make money. Sadly Firefly has a track record of not doing that very well. Boobies and serialized content have been doing quite well. Somehow I doubt Joss will stoop to the boobies level. As far as I can remember the only time Joss has included nudity was a brief scene in Cabin in the Woods.
Actually IIRC it had a pretty large budget for a TV show. It was a fairly expensive show to make and brought in so little ratings that they had to refund advertising money. So, basically a double whammy.
Yes, arguments can be made that things would be different this time, but arguments could also be made that a brand new show without a bad track record could be just as good. Firefly has a stigma of failure to overcome. A new show just has to sell a dream.
I thought that about Firefly's budget too, but Joss said the opposite in one of the introductions in the companion books. He said Buffy, at least by the later seasons, had a higher budget.