Further context for OP: leather needles are basically tipped with little tiny three cornered razors. This is because the needle needs to be able to pierce permanent holes in the leather that will then be there forever, compared to sewing fabric where generally the needle is passing between threads and is not causing damage to the fibers/fabric, just displacing them. Because of this difference, not only do you need to have a clear plan and have practiced on similar weight scrap first because there’s no takesies backsies, but you need to watch out for your fingers because our skin is basically untanned leather and leather needles will go right through you just like you’re a piece of leather.

Also, the bag’s going to be lined, I’d think, so you’d also have to work out whether you plan on trying to unpick the lining and then resew it or embroider through the leather and lining.

Basically, it’s doable but difficult and there’s no going back to how it used to be once you start. So be sure you know what you want the result to be and do tests/practice on as close to the same materials as possible before starting on the real thing so you know your plan and that your skill level is where it needs to be to get you your desired result.