As long as their current configuration passes DOT laws, I doubt you have a chance in hell winning a lawsuit. Of course, if you take into account the stupidity of the court system, anything is possible.It's interesting that two of HD's newest, and most popular models, have eliminated the tail light altogether. Bot the Nightster and the Rocker have integrated the tail light function into the turn signals.
I'm used to customizers removing safety features for the sake of style, but for a major manufacturer to do so suprises me. I wonder how long it will take before somebody gets hit from behind on one of these bikes in the dark or fog, and sues the crap out of HD. If they do, I'll bet they win.