Are you sure? Within the physical limits of the lifter system, the ramp opening rates are not fixed across the spectrum of cams are they? So if it is beneficial to your application to open the valve at a faster rate and you accept the consequences for that (spring rate, wear, reliability), you can spec a more aggressive cam lobe rate. Some cams with .500 lift and X duration look like a pointy cone, while others with a more aggressive ramp look like a Montana butte, vertical sides with a flat top. You need a roller lifter to accomplish the more aggressive acceleration rates and I'm sure that there are other limitations such as base circle diameter, lifter diameter, and such that limit the rate within a given scenario. If I'm wrong I'm wrong.