It seems to me that Sterling owners are very loyal to the brand. When I play walkon games, I sometimes get the question why I still use the first marker I ever bought as my main marker. I usually don't have a good answer, but I think it's because I haven't found anything that compares to it, regarding ease of use, accuracy and the more subtile but oh so important feeling you get when using it.
So if us oldschool sterling owners get some upgrade options like things that have been mentioned in this thread, I think it will payoff in the end with an even more loyal costumer base. On the other hand, I have yet not needed to buy a single replacement part for my Sterling (with the exception of orings). It still runs with all parts that came with it when I bought it second hand back in 1998. So spare parts might not be the best way to get rich quick regarding Sterlings. But upgrades is something that everyone dreams of in secret I think.