Then we'll just have to disagree. Steel might be 4x heavier than horn, but when you need significantly more horn than steel to achieve the same results, then the supposed 'energy efficiency' of horn disappears.
Toady's has implemented a material system, and that data is where the traits of the weapons in question should come from down the line IMHO. Not from arbitrarily and artificially making non-horn projectile weapons worse by treating their quality as less.
Now the main barrier to that as I see it would be that DF does not currently really handle items made from multiple materials very extensively, and doesn't handle composite materials -like yew or a horn/sinew laminate
at all. Toady would need to address this at some point or I imagine any *Water Buffalo Horn Crossbow* we get down the line will be sorely lacking in power, I fear.
Another would be that DF doesn't really distinguish horns from hooves, but while a bull's horn would be a great material to make a composite crossbow out of, it's
hoof....would not
The last problem I could see is that different materials having different draw weights could cause some problems for bows, which do not have crannequin's etc that would allow very weak dwarves to draw back the crossbow string. If you stockpile a bunch of different composite and wood bows, they could all have different draw weights, which could cause problems for the military-like having 20 different bows that nobody can use because their drawstrength is too high-or your strong dwarves taking the weakest bows, thus depriving your weakest dwarves of usable bows...too say nothing about the potential problem of siegers/npcs spawning with bows they might not be able to use.
Now
what I'd like to see would be:
1) Frames and limbs made separately like the components of instruments currently are.
2) When queuing up limbs to be made, you should be able to select what how strong/weak the bow/crossbow will be, as well as the material. Possibly by selecting a material and then from a list of valid draw weights (measured in kg/urists/whatever they are called) selectign a material but not a draw weight or material will result in the bonecarver/weaponsmith etc making limbs at a draw strength around what an 'average' dwarf of average strength would be able to draw, or as close as they can get with a given material. Selecting a draw strength but no material will result in dwarves only selecting materials that can achieve that draw weight, and selecting a material but no draw weight will result in the construction of limbs for crossbows as close to the draw strength as they can get with the selected material.
3) Depending on the draw weight, crossbows and bows could be classified as 'light' or 'heavy' depending on if the draw weight is significantly higher or lower than what an average member of your fort's species can use-similarly to how clothing can be labled 'small' or 'large' if it's too small or too large for you (in adventure mode) or your fort (in fort mode). This should help the players sort out bows and crossbows that might be useful to them.
4) If a bow is too strong a draw-weight, you can't draw it, but perhaps crossbows could have longer reload times in tics based off their draw strength as a balancer vs bows. This could make crossbows better as a sort of siege defense weapon vs bows, with their faster firing nature, might be better for skirmishes in the open. Players might also value their stronger dwarves for their ability to use heavy-draw bows, which would be neato, I think.
5) Invading archers should be generated with as strong a bow as they can pull, to prevent them from coming with bows they cannot shoot or bows much too weak for them- invading crossbowmen should be generated with random draw-strength bows, since their strength shouldn't impact their ability to load or fire their crossbow.