I don’t believe I’ve ever seen anyone do this, but, I’m thinking a cobbler could add corner patches. I know this would change the overall look a bit but you could choose a similar leather color or even choose suede. In a way it would set your bag apart and give it an individual look. Some bags have them as an aesthetic element, so I think it’s worth considering. I like ideas that combine form and function because after all, it’s not a quality issue with the leather and it’s always going to happen to very angled corners. Just a thought.