on warband morale:
its not a matter of where you recruit troops from or anything, its a matter of who you are fighting. Nords dont like it when you fight nords (and thus, all nords in your party get a morale penalty, making them much much more likely to desert).
Just by waiting decreases this, so sitting in town doing nothing for a week will give your nords considerably more morale..
I believe it is only controlled by lord-type (a nord lord in theory always has nord troops, so fighting him decreases nord morale, even if he happens to be full of mercs), although its possible it goes a step further than that to look at who you killed in a battle.. I havent done any real testing on the matter, just playing.
Of note: Mercs never have morale penalties for fighting mercs. (if that is because there are no merc parties, or because mercs dont have a faction type or whatnot, i dont know)