Here are a couple of ideas for repairing old gangs hit by previous bugs, without needing to make huge changes to the game's code or roll out a dedicated patch:
Gang Infamy loss/corruption - Please add new Infamy goals for defeating 150 of each type of ganger, then 200 of each, then 250, then 300, etc. Perhaps up to 500. Adding these extra goals (with a reward of 15 Infamy for each) will allow older gangs that were hit with huge Infamy-loss bugs to gradually reclaim that Infamy over time. Cap max Infamy at something like 350, to balance this out. I saw you added a new Infamy goal related to Van Saar, so it must be fairly simple to roll out a few more goals.
Lost Max Skill Points - Please add a new consumable item that appears in the Shop whenever it resets during Operations. Price this item at 5,000 credits and make it equippable/useable by Rank X gangers only. If a ganger uses the item during a mission, then after that mission they gain +10 Max Skill points. This will allow all players who lost a lot of max points to regain them, and give the Rank X gangers in high-value gangs something to spend their credits and XP on. If you can't block lower-Rank gangers from using the item, limit it so it only appears in the Shop during Hard and above Operations.