If you want the weapon to scale with the character so that they keep it for longer, I would design the weapon to enhance the skills the character unlocks as they level up.
At 6th level Rangers can choose another Favored Enemy, so having the weapon do even more damage (+ half your character level piercing damage) against their favored enemy is a nice way to enhance that.
Increasing the critical damage range of a weapon (18-20) instead of the usual 'just on natural 20's' is a nice way to make a weapon more popular with players. even if other weapons they find might do a few extra damage points more consistently, having a higher chance at 'burst' damage is fun and a bit more dramatic from an RP perspective.
One key area that limits the damage of bows and crossbows is loading. Artificers can craft a Repeating Shot weapon that essentially self-loads with magically created ammunition. This is a neat trait that can make a weapon more appealing than others as you no longer have to constantly load (which reduces overall damage output) and you no longer have to worry about running out of ammo if it is difficult to restock.