I don't know about anyone else, but if I'm at a dealer that doesn't know the options on the vehicle they're selling I'm not so likely to buy from that dealerI don't think they can based on how you buy a car at a dealership. You usually start with a base model and then add RPO numbers to it. The salesman would just say 'this much' for the SS option and 'this much' for the RS option. He would not care (or know the difference) about what you get when you pick an option.
It would be foolish to NOT have the RS package on the SS be priced differently. How hard could it be to add two RPO numbers to the system? One for use with the LT and one for use with the SS. I'll certainly be in the market for an SS/RS (possibly a 'vert if the price is right - especially since it's excuse to wait for the HUD) - I can only hope (and assume) that GM is smart enough to not try to charge its customers multiple times for the same options.