Well, your reinfocements are no worse off than your AI opponents . . . so at the worst, it is something of an equalizer. And I will gladly accept a few extra casualties on occasion for the chance to get 2-4 armies in battle at once.
Besides, as you pointed out, you have the option in M2TW. That's the big thing I (and I believe alot of other people) are asking for, the choice. If you don't want the troops under AI control, you don't have to put them there, and instead can simply have them reinforce as they do currently. But for those of us that prefer to be able to bring large armies on the field, we too would like to have the option, at the very least, to put the army under AI control as in M2TW, and preferably to be able to give it basic orders is in Kingdoms. I, and others, find the bigger battles more immersive and, in their own way, more interesting.
Bookmarks