As the title says, did anyone find a way yet to make client states/ puppets give you more units to levy?

I know in Rome II it was tied to the technology that unlocked champions and I tried finding an equivalent for Attila with no success. Another option I tried was giving the Sassanid bonus from the trait "King of kings" to other factions but I couldn't make that work as well. I really love the way the "Moar levies"-mod for Rome II let you diversify your armies with other cultures units and I hope someone with a better knowledge of modding is interested in this as well.