Champions And items Balance

so I have no idea league balancing works but is it difficult to just adjust items and champions based on the game modes. make it so bard chimes spawned faster in nexus blitz or more on his side and just leave him like he is in summoner rift.

or make it so kassadin consumed less mana when ulting in aram then in summoner rift . is it possible to separate the champions stats between game modes. same with item.