Not exactly thrilled to enter "discussions" of what map ought to have the bonus... and 100 monsters for 50% bonus is incredibly large given how RO is a serious grind game and even my alt farming only knights can stay at bathory for liek 600+ and not go back to town (and many, many better knight players than me exist).
And the other question: is this even do-able without drastic dive into source code, heh