Though I decided against Sabretooth for my game due to plot reasons and him being so close to Logan, one of my suggestions would be to set him to "Wrestling" melee style like how he was in X-Men Legends 1. This would at least make his melee attack style functionally somewhat different. Slower yet stronger. Maybe also give him a charging move like Colossus' to replace one of those copy/paste powers he got from the "runt".