Thats true. It is very hard to get people to help out with a playerworld that is not online yet.
My advice is to do what I did. I built a large amount of the levels, npc's, and graphics. Once you get a large amount done that is when you may be able to get others to come around and help out. While others are helping out you can go back and do some touch up on the levels.
Your idea sounds kind of good. Only thing is I don't know if people would be too thrilled to pay 10G to pk. If I play on your playerworld get ready to jail me because I won't be paying to pk.
