I'm aware that the time and effort needed to level grind Amelia is rarely considered worth it, but even so General is considered her best option, especially in Creature Campaign.
Having played Fe8's creature campaign very recently I can say Great Shield has saved my butt several times from magic users and Draco Zombies.
Plus would you want another Great Knight option or a unique, more fitting promotion for Armor Knight. I imagine if Cullum for example, promoted to Halberdier he would gain a massive increase in speed and skill but no defense boost. The defense cap would also be much lower then Generals of course.
Hopefully this means Soldiers/Sentinels are playable and the green units aren't in NPC only classes.