well, problem for me is not the size. I liked the first huge battles, its kind of epic. But the whole system is bad, big battles should have an impact.
Soldiers where killed on both sides and then they continue like nothing happend.
Well, no matter how big the batttle is, every lord and their fiefs should get a "recruiting block". Less time for winners ofc.
Maybe also a "moral influence" to the kingdom with effects on declaring war and things like that