I don't think this is a good idea. First, balancing ranged weapons should wait until there's a larger effort to balance weapons -- the game simply isn't balanced right now, and that's that.
Second, this would mean that the best crossbowdwarf in the world, armed with a shoddy crossbow + bolts, is not even the slightest bit better than a barely-trained recruit. That is both unintuitive and, in my mind, silly.
(Third, of course, I kind of like having bows and crossbows so deadly. Dwarf Fortress is supposed to be deadly. An accurate crossbow is every bit as deadly in real life. Now, thrown vomit and coins, not so much... although it would be cool if the existing deadliness of thrown weapons was retained for legendary throwers. It's fun to be awesome at something, when your character actually has awesome-level skills; I would be disappointed if the ability to throw a coin at someone and have them fly back twenty feet, hit the wall, and cause their chest to explode in a fine shower of gore was taken out. It should just be reserved for the legendary thrower who will be remembered for generations.)
An adventurer who enters a goblin fortress unprepared can frequently get pincushioned immediately; I like that. There was a story a while back about someone who slew a dragon by incapacitating it with his first lucky spear toss, then choking the dying beast to death. I think all those things should still be in the game (although that throw should require a fairly heroic-tier character or extreme luck); they're a big part of the Dwarf Fortress setting to me.