I would drop Lynch for Helu......
I think Lynch will improve slightly once Rice gets settled into offense and once they bench Tarvaris Jackson for Whitehurst. However, I seriously doubt that he will ever make it off your bench.
Scott is going to take over for Benson during his 3 game suspension, but once that is over, Benson will resume his role and Scott will resume his role. So Scott will not do anything for you when Benson returns.
Helu is the future in DC. In my opinion, HIghtower was signed as a cheap placeholder until Helu gets his feet wet. As we saw last week, HIghtower tired a bit and Helu filled in nicely. Even Kyle Shanahan said that Helu has earned a more prominent role in the offense. I fully expect to see Helu taking the bulk of the carries by mid-season, while HIghtower is relegated to 3rd down duty and in other situations.