I also find Versatile a weird design choice to try to represent that way bullets (especially the rounded bullets of early firearms) have all this kinetic energy, but can also pierce armour and flesh like the best piercing arrows. Damage types remain an abstraction, but I cannot imagine any ancient firearm being only Piercing OR Bludgeoning.
When I was designing my gun houserules for a campaign that launched only a few days before the playtest, I tried to bring this dual type idea into play with custom weapon traits adding bonus Piercing damages to the Bludgeoning base damage of guns :
Point Blank = The weapon gains a +1 circumstance bonus to damages under the noted range* (usually half the weapon's base range). This damage increases to 2 with Greater Striking Runes. This damage is always Piercing.
I also went for a Piercing splash damage for Scatter weapons.
I am wondering if that kind of bonus damages through traits could be a solution for the apparent problem with a weapon doing two damage types at a time. This way, it's no different from having some Fire damages added on the Slashing damages of your magic sword.