Easy
1. until the repeater bug is fixed just make repeaters behave like a regular xbow but have 3 bolts hit instead of 1. It is less pew pew cool but game mechanically it works out better.
2. have house D sell returning silver bolts OR add returning silver ghost touch bolts to the silver flame vendor
3. make flame arrow wands have 3 charges max, but each cast of flame arrow generate 1k bolts/arrow
it in no way overpowers the spell to save 20 wand whips at the start of EVERY quest where you want to use flaming arrows
4. make halfling thrown damage enhancement apply to xbows also
Slightly Harder
5. Add a feat to rogue special feats that increases the sneak attack range by 15 yards and have ranged attacks bypass 10% fortification, this would be the ranged equivalent of opportunist.
6. add checkboxes to quivers so that you can choose to autogather either bolts or quivers or both
7. add checkboxes to quivers to add "found" projectiles to the top or bottom, so I can use up bolts I find instead of carrying them
8. allow arrows and bolts IN quivers to be added directly to your hotbar and to switch to those arrows/bolts when you click the hotbar button