Damn! i know theres must be a way to leveling those BBLv!
btw, the point is, u able to lvl up the BBLv if u fuse the same element type, doesnt matter the level, its still able to have the chance to lvl up, also, BBLv doesnt use Exp but use chance. But it is true the higher lvl the unit that we want to BBLvup to, the lower the possibility?