welcome to the forums.
Your questions are interesting. I'am myself are quite new to FC, so take my answers with a grain of salt.
The reason to take a crossbow over a bow are many.
1. Easy to handle as a weapon. Where its point, there it hits.
2. It goes through armor like butter.
3. A bow is nice, but you need time to string him up with a sinew (I hope the sentence makes sense). You can't go around with a stringed bow all the time, or you run into serious problems).
4. Rain can mess up the sinew of a bow.
4. It needs time and dedication to train an archer. So not even any hero should go around with a bow
Bandoliers can only be used to lower the load time of gunpowder weapons, if I remember correctly.
And to change a ammo hopper seems to be only a free action. I didn't found anything about such a device and how much bolts it could hold in the FC books. But the chu-ko-nu (hopefully written right) could fire through a load of 10 bolts in 15 seconds, so 10 bolts per ammo hopper seems ok.
Historically, if I remember correctly, crossbows were aimed at an enemy and fired. No fancy things needed with these beasts. But the chu-ko-nu (asian repeating crossbow) was used to fire indirect and lay waste to an entire area - therefore hundreds if not more were used in unison.
If you want to emphasize the use of a crossbow over a bow there are many options at hand.
1. Make bow forte a requirement for any bow - maybe with the exeption of short and pellet bows
2. Use STR 13 as a requirement for any bow - with the exception of short and pellet bow, you could apply for these two a STR 11 requirement
3. Up the damage of bolts by 1d6
4. Make up some feats for crossbows like:
Benefit: Your crossbow bolts gain 1d6 extra damage and Bludgeon. Also you gain a stance.
Stand your ground (Stance): You gain a +2 damage bonus against standard characters.
Benefit: Your crossbow bolts gain AP 3 and Bleed.
Pepper the Bold (Trick): If you hit a character by 4 or more, you hit an adjacent character with your attack, too.
Benefit: Your load time decreases by 3 and your crossbow bolts gain Excruciating.
Punishing the Undying (Trick): If you hit by 4 or more apply the damage twice. If you hit by 10 or more apply the damage thrice. All damage is seperately rolled.
I hope this helps Oniya. Beware that I made the feats, stances and tricks up as I wrote this reply... they may be unbalanced. These changes should help to facilitate the difference between bows and crossbows.
If anyone sees so, please feel free to correct this.