Battle System changes refer to the revamping of the current "Cross Class" system because of it's restrictions when becoming jobs. The restriction being that currently a job can only cross-class from 2 other classes, but since HW and now SB are job only, cross-class becomes an archaic system since it provides 0 means to be able to cross-class from those 5 jobs.

The other change is re-evaluation skills and abilities in the game and removing them based on how useful they are, for example they noted Fracture as an ability that could either be changed or removed because as it stands for a lv 60 WAR it's ability actually hurts WAR's flow rather than assist.

But I believe those are the two main points, they aren't going to remove the indicators for attacks or anything like that, battle revamp relates to changing the current "Cross-class" system and cleaning out class/job abilities that have become outdated/useless.