Glass Cannon is only effective in battles and when you look at it as a whole GC with haste is useless since the max AP any character can have is 20 and almost no one has that until near the end of the game if they even wind up having that at all. The fact is most characters have a maximum of 12-14 AP for most of the game, So Haste Plus the base will always max out or just about max out a characters AP every turn anyway.
You are wrong.
Haste increases max AP by 4 (8 if GC) and recovery AP by 3 (6 if GC). Thus, haste will
never cause you to max out AP, with or without GC, unless you were maxing out AP per turn without haste anyway, since the bonus recovery AP is
less than the bonus max AP.