Sort of like, instead of ignition boost, Byakushiki would get multiple sets of boosters. It's mostly rule of cool, but in terms of practicality, it's for Ichika to slowly master the speed. The first set is the basic which already outclasses 1st shift. Then as he progresses in control and the current booster set can't handle anymore, the next set becomes accessible. Kind of like that I guess.
I wanted something that could replace Setsuna, but I'm not even sure if I want to completely get rid of Setsuna.