The problem is: these guys aren't foundational to how these companies work. Killing them might cause some confusion, and even make it so the upper management stops squabbling for personal gain for a decade. You'd probably strengthen it.
If, by some miracle, you do cause the whole organization to unravel and split up: you'll likely get a repeat of standard oil, where the new companies combined expanded so much quicker and made so much more profit. Just like how pruning a tree makes it healthier and grow with more vigor.
Better to let the rot start from the roots.
The amount you'd need to get rid off would put you in territory or pure fantasy though. Also, the government would probably step in and force a merger.