Not really an answer, but I'm just wondering where you've got the idea of 'huge' Carolingian armies from? Almost all of what I've read on Carolingian warfare suggests very small army sizes, certainly never really going over 5 figures in terms of manpower. The only scholar who seems to take a different direction is Bernard Bachrach, and his stuff isn't entirely unproblematic...

(Hat-tip to /u/textandtrowel so that the bot doesn't ping me!)