Honestly lol the more I think about how the Legacy system is set up, the more it occurs to me that it would already work really great with a cash shop system. Most of the prices for simple unlocks are outrageous, especially since many of the new ones are per character only. With ridiculous Legacy prices for unlocks, you could already have the system of: "You can purchase these things in game for a few million credits, or you can unlock them for ten bucks on our shop."
It would keep the fairness that anything can be earned with in-game time and effort, but that it would be easier and quicker to just spend a few dollars and get it an alternative way.