Well first off, Enemy Mobs/NPC's will most likely be animals such as wolves, bears, and even stray cats. Honestly, it wouldn't make much sense for us to make it so that if you killed a wolf for example, that you would just gain yen. If anything we may make it so that they drop pelts, which will be able to be crafted into equipment by certain professions, or possibly sold to a certain NPC.
On to the next suggestion, if we added in player bought houses we would have two major problems. First off, in samurai champloo, if someone really wanted to enter your house, a locked door wouldn't be enough to keep a samurai out, they'd simply force their way in. also, if someone were to die, their house would remain on the map, yet it would no longer have an owner. This would mean that by half way through the wipe, if everyone had a house, we'd have a large portion of wasted space on the map.
Thank you for the input though, it is much apreciated.