Materials for a bow wouldn't be hard. Wood would (woodwould?) be scarce, as would many 'traditional' materials. However a composite (not compund) bow can be formed from many different materials (http://en.wikipedia.org/wiki/Composite_bow). bone, steel leaf springs, gecko skin wrap etc. The damage could be scaled according to the materials and quality.
As far as the skill learning curve, it's rough. Then again so is learning the finer points of explosives or medicine. Any body who can pick up rifle can learn (yes learn it has slightly different skill set) a crossbow. A bow should require a background / perk because of the very different skills required.
Crossbows and bows could be treated seperately as far as weapon tiers go:
A basic survival made bow / a well crafted hunting bow / a war-bow (see Agincourt) / grizzly killin' feather death machine.
Basic stick on a stock / hunting x-bow that has optic and cocking gear / boltcaster (Mad max / Cyborg) / manportable balista
they should really add bows to Fallout 4.....
but, although F:NV has been finished, could they have added bow, and hid it somewhere?
maybe, they're keeping secrets :whisper: that bow has been already in the game.....
in Oblivion, me and my bow are best buddies, as i can kill a bandit with a single shot.