I think the first priority is how to avoid the ugly mishmash of elements that Second Life was notorious for. Probably Metaverse will have the same problem.

I like the idea of allowing people to vote with their feet. Cool places should organically attract more people and grow larger, while ugly places should dwindle away. Maybe a developer's license can be had for a fixed fee, and the amount of land you have to develop on is a function of how many residents you have. As more people move in, you get more land to develop on.

Then the next issue would be how to manage geographic linkages between developers.