Your leather is already heavily coated. I would imagine any kind of spray would just drip and run off the surface. If my bag had that kind of finish, I would just leave it, just as I would likely leave patent alone.
You may want to test your bag's surface, for curiosity. Just flick some water from your fingertips and see what happens. I would suspect the only way water would truly penetrate your kind of bag is through seams or crevices...that would be a vulnerability for virtually any bag.
Thank you very much for the advice and info!

