I like the idea of requiring a repair kit to repair weapons. In RP terms it is valid, but having them be only a single use?  Please consider increasing the number of times you can use them.  Perhaps a random number of uses or even a random chance to destroy the kit dependant on your skill in the repair weapon skill set?  Surely, a player with a higher repair skill can use a kit with far less chance to damage the kit(sharpening stones and such) than a player with a lower repair skill.

If this is an attempt to remove money from the economy, then just up the price of the kits proportionally to the average number of times you expect people to be able to use them before they are ruined.