I believed our original idea was that Xana and Xano were not greedy, they only had a vision of the world that was far different from Amon's. After Amon's conquest he left many without bending, and I don't believe Korra's put it together yet that she can try to restore most of the city who lost it. I was going to bring this situation up with Bolin in the next skip because it provides Korra with her own small arc of what to do, since not everyone deserves their gifts since they used it for evil, but what if they worked for redemption? Just something for her to think about. 

Anyway funding for their projects is probably costly so I can see Xano taking bribes for bending again for certain criminals, and possibly doublecrossing them later with a temporary mixture rather than a permanent one. No matter what though, Xano has ambitions that aren't entirely good and Xana is the one who will work to stop him later on. If Lin and Tenzin get the mixture from Asami, I can't see a reason for Tenzin to take it. Any reason Lin might?