Can it be done, it's possible. I've seen it done on occasion. Most of the re-dye jobs I've seen bled and rubbed off on folks clothes when they sat down on the couch. A friend of mine owns a upholstery repair shop and never recommends re-dying leather and even told folks it would be cheaper to replace than re-dye. The reason was the factory finish would have to be removed for the new dye to take. The leather would then have to be sealed to prevent the dye from rubbing off.
That said, since you're not planning on using it for furniture. I would try cleaning it with mineral spirits. Allowing it to dry thoroughly and use a good dye like Fiebings.
Also, if you're using it from sheaths and bags, you might try passing it off as brain tan since it was possible to make brain tan white.