In Phantasy Star:generation 2, each character has a new special skill that can be used in battle after charging up. Limit breaks, essentially. If PSIII and PSIV had been remade with the same feature, what limit breaks do you think each character would have? Let's even include PSI, since Generation 1 didn't have that feature.
As PSP mentioned, I think it would have been good for Chaz to get a special that calls up all the past heroes -including Alys - for an attack (possibly with bonus healing from Amy's turn).
Lyle could transform into a dragon for his special, though that might not go over so well with Rhys.