[M]y worry is that the weaker spring will degrade with time and fail to fire the primer in the future.
All springs will degrade with time and eventually fail. That's why part of pistol maintenance is the periodic replacement of springs. To my knowledge, CZ has not published a detailed maintenance schedule, but SIG Sauer has, which can be used as a surrogate. There's nothing preventing you from changing your springs at a more frequent interval if that makes you comfy.
To compensate for the lighter hammer strikes their upgrades produce, doesn't CGW provide an extended firing pin? Presumably, the extension isn't long enough to defeat the firing pin block.
