Ive been using 'TweakMB' to adjust certian game aspects easily in warband. I recomend it. Ive been playing around with the number of bandits that spawn and their group size. For instance, sea raiders come in armies of 50 to 200 but can only have a maximum of 10 armies in a 168 hour time span. So there isnt many, but when there is its like an overseas invasion. Looters have been set to be in parties of 1 - 50 with up 250 groups on the map at one time. And my fav are the steppe bandits, charging around in hordes of around 100 - 150. However, i have had to adjust it a few times because the bandits have been either been dominating the map or have been totally wiped of the map. So i havnt found the best balance just yet. But its nice to have to keep an eye on them, as if left untouched they can build up to concerning numbers, likewise, hammering them frequently keeps your area of the map nice and peacefull. Its also easy with TweakMB to quickly adjust it all.
And its not just the bandits you can change, there are other features like changing the amount you can bet in tournaments and recruit rates etc. I did have the taverns set to always buy prisoners, yet since i updated to v1.05 that feature no longer works. Which is a shame. Otherwise, its very handy.