Current system is such that when you limit break using the same 5* hero you get + levels on your base hero.
Even when the material hero used is a Limit Broken hero, this remains the same.
Would it be possible to increase the number of limit breaks if you use a limit broken hero as material?
Eg.
LB +1 Kai (Base) + LB+1 Kai (Material) = LB+3 Kai instead of LB+2 Kai.