If anything, the secondary pistol needs a bit better range, in my opinion. Far worse problem is that the Weapon Special is only used by the Rapier (to shoot the pistol) and by Waystalker (to change zoom). This leads to new players not even being aware of it, and even when people find it, never actually learning to use it. By adding more use for the button on different weapons and characters, there would be more reason to learn the whole mechanic, and through that to use the rapier’s pistol better.
A starting point could be adding an optional zoom to Sienna’s Bolt Staff and a few other ranged weapons too. A bit more creativity is needed for additional use on melee weapons, but axes (and pick) for example could well be used to hook shields, immediately throwing the opponent off balance but not doing any actual damage, thus (among other things) making a few weapons better at dealing with shieldvermin. A murder stroke on greatswords for dealing with armor might be fun too.