I have a somewhat different conception of how Repair should work (though I'm not exactly sure how to implement it...).

Basically, I think every level in Repair should allow you to repair, say, just a single item (from say about 50% wear) over a 12-hour period.

The problem with Repair as currently implemented as you say (and in my opinion too) is that it's too easy to repair virtually all of the items you wear (and even in your inventory) over a 24-48 period with just 1 or 2 levels in Repair.

So I'd like to see Repair cut down so that it's more like: 1 Level in Repair fixes 1 item over 12-24 hours, 2 Levels would allow you to "fix" 2 items over the same period, 3 Levels = fixing 3 items, etc.

This would actually require Fighter-type builds to put probably 5 or so Levels in Repair before Repair would be truly useful.

Your suggestion is a different approach that would also work.

But, as implemented in Book II, Repair was definitely overpowered...

Repair could be weighted by your character's training. You could say that the training includes learning about the maintenance/fabrication/repair of the equipment associated with that skill.

For an example, a character with a 10 level in bows would be more proficient in the care and maintenance of bows and missiles compared to someone who has a 10 level in swords. The character with the 10 swords would be better at repairing swords than the archer.

This would apply in the same manner for the various types of armor (light, heavy), shields, and other items that wear.

Magical things don't usually wear with use. But characters that have good intelligence or wisdom would be better at maintaining magical items compared to a character that is mainly a fighter.

You could also add items that are found or bought that could improve your character's repair skill (e.g. The Encyclopedia of Bows and Arrows (manual of repair), tool kit +2, Shield Making for Dummies).