The repair system in 3/NV wasnt particularly deep, but with some minor adjustments I found it to be pretty cool. The biggest thing for me was having jams happen on firing aswell as reload, and having a substantial chance of them happening below 80% condition.
It was pretty cool for the realism/RP mind that I like but then it added some more problems to the gameplay. It made me significantly more powerful compared to my enemies, since it was easy to keep my weapons in prime condition in both games, whereas raiders don't have the luxury of being a PC. Since it effected the raiders just as much as it effected me, they often spent more time trying to clear jams than actually firing at me, lowering the difficulty a fair bit.
In the 7 years of playing Fallout 3 and the 5 years of New Vegas I have never once had my main weapon break on me. Even now with the forever characters with a realistic amount of weapons to carry, they have never been put in danger despite heavy use of their small amount of weapons. Really im not sure what a good all-fitting solution to it would be. I go for realism and RP, so I liked the heavy jamming, but then people who play for challenge might dislike that for the reasons ive already said. Some people also dislike having to spend time on upkeep, and prefer the game to be more focused on solving quests or action fighting. The time not spent solving quests for them would be dead weight, and this ties into a whole bunch of other gameplay mechanics that are not even related to weapon repair.
Bethesda has a pretty tough job, making a game that everyone can enjoy equally. I think they must have tried a whole bunch of different solutions to this problem, and ultimately they know how the game works and doesn't work better than any of us here. I hate to do a appeal to authority, but from where I am standing I just can't see any solution to add more onto the system without causing a imbalance in how its enjoyed by the large variety of players that has made the game a powerhouse.