Damn near every online game already has these tools in some form; they just restrict them to the developers by making sure that only developers can use them. Sure, some tools require more knowledge to use than the average gamer possesses, such as using a scripting language, but many tools can be easily handed off to players with some simple modifications. Now, that list might look like a lot, but is that really so much to ask for, when most of the tools are already built?