Do people deploy PoS chain clients that are ok with blocks that totally ignore the historical leader schedule or use a leader schedule that could not have resul

Do people deploy PoS chain clients that are ok with blocks that totally ignore the historical leader schedule or use a leader schedule that could not have resulted from the distribution of stake in the network at the time? If not, how will the attacker who wants to swap out a single block a year later get all the other validators to sign a year worth of new blocks?