I just beat the game for the first time. It was, awesome, but I mean, there is something that I thought would be cool. You could add greater enemy variety or something to make up for it, but I like the idea of being able to customize my characters to my play-style. I know that may not be the premise of the game...but I mean, what if there was at least the option to make at least one person customizable?
I really love this game, and most of what I would like has been said, but make it so you can use the potions that give buffs before battles, using up an entire turn to use a potion that some only last one more turn after is not helpful in battles where you might actually need them.
Also in addition to this, I would say add mini-boss encounters, but make their little symbol different from the normal ones so you know its coming, like the artifact chests.
 "Arkandian Crusade"){kind=icon}
 "Wondrous Lands"){kind=icon}
 "Reactance 2"){kind=icon}
 "The Enchanted Cave 2"){kind=icon}
 "Dawn of the Dragons"){kind=icon}
It is nice idea, but we initially didn't planned it.