Yeah! Join! We want Join!
I mean, right now the "easiest" way to do stuff like that is the Bruges Tower method; "putnpc and destroy" NPCs, but you have to pass in all the variables with X,Y and image...if you wanna have a boy and a girl NPC with the same basic code, you're screwed.
Dun see why it wouldn't be possible on clientside "free" servers, and it's not a payable advantage really, the players would never notice, just the developers...
