Well Mike, I may as well just copy Hawg's reply to your question for the most part. Since I consider modern caps as the real problem, I don't care to modify the guns. I am even a long time avid Cowboy shooter, but one who approaches things from an historical standpoint. However, I don't shoot the percussion pistols exclusively. With the already mentioned attention each gun receives, cap jams are not frequent. Admittedly, though, right in the middle of a Cowboy Match is not the time to be experiencing a cap jam! I fully agree that a light, smooth action is a joy to use, but if a heavier mainspring will almost eliminate those last few cap jams(on the few guns so prone), so be it. Since I don't participate in Cowboy matches worrying about my final Match Standing, what makes me happy is a nice clean presentation as close to period correct as reasonable.
I just saw on another site where someone is approaching the modern cap problem by making his own thicker caps on a 3-D printer! So far no report on how they are working. I would be willing to accept caps made of a different material since the modern cap manufacturers don't seem inclined to address the issue.