I think a key thing in general, is that crossbows should be much cheaper than longbows. At least 33% less, maybe half, or even less. To reflect that they require little training. Balanced by being less flexible, weaker in some areas, and/or requiring more tech investment to build initially.
Possibly, the tech path could also be more divided. Crossbows and Arquebus would be the ranged attackers of choice, for those who go down the metalworking and industrial paths. Whereas archers, longbows, and marksmen, could be more closely tied to the recon line.
Some thoughts on tech tree paths:
Archery, requires crafting
Bowyers, requires tracking and archery. (no requirements in the metal line.)
Poisons, requires hunting and archery
Precision, requires poisons, bowyers, and tracking.
Crossbows, could be moved back the tech tree a little. Perhaps requiring Engineering and Smelting or Iron working. Engineering itself requires construction and mathematics, and smelting needs bronze working.
Machinery should lose bowyers as a prereq, to unlink those tech lines. Instead requiring engineering and iron working.
I'd say, arquebuses should require both machinery (to mass produce the guns) and blasting powder (for the gunpowder), and be proportionally stronger to compensate for the increased tech requirements.
Collateral damage does seem like an interesting idea for them, but I think the ability to cause fear is a primary thing. in the case of Guns versus Swords, the loud explosions and people invisibly dying are key tools, gunpowder weapons attack the enemy's morale as well as their men.