I've heard Ritual Entertainment is no more and even though it doesn't mean they will now allow you to do as you please with their SiN games.. perhaps they won't mind so much. In fact, a really good fan-based game could potentially generate new interest in the brand and so on.

I think however that reinventing the SiN universe as a fan-based project could be extremely interesting. Like a cell-shaded version with all chibi-style characters (big heads, small bodies), totally over-the-top humor in it or something like that.