Artifact crossbow Thunderclap, which fires either lightning or lightning-enhances the crossbow bolts it fires, and you can invoke it to create more bolts.

Make the Longbow of Diana able to change shape between the different types of launchers (bow, crossbow, sling), either by invoking it or simply by applying it. This allows Rangers to play with whatever type of ranged combat style they prefer, and allows gnomish Rangers to use a crossbow without being coerced into switching to bow later.

Crossbows deal more damage than bows, but the multishot bonus is lower because they are slower to reload.

Note a similar implementation in dNetHack, where crossbows always only shoot one bolt but the multishot amount multiplies the damage of that bolt.

Some Yendorian Army monsters, particularly soldiers, are eligible to receive bows and crossbows as starting weapons.

Merge crossbow and bow skills so that gnomish rangers don’t get hurt by the lack of ammunition.

Gnomes get a racial bonus using aklys and crossbow. Should probably be implemented by affiliating an item type with a certain race, adding this as a new object attribute, and only specifying it on racial items (elven armor, orcish weapons, the aklys and crossbow, etc.)

Make the Ranger quest artifact a crossbow if you are a gnome.