A couple of scenarios:
*) A shop (or, in general, economic) plug-in may need to regulate access to its resources in some ways duplicating or competing or contrasting with an area protection plug-in. In the best of possible worlds, the former plug-in could query the presence of other plug-ins covering similar tasks and co-operate with them, by query them or whatever.
*) A package of specific 3D objects (say, a collection of buildings, or of vehicles, or whatever) may be released. Several plug-ins may include them in their own assets (duplicating resources and making maintenance of the 3D object harder) or the package may be a plug-in itself and other plug-ins may 'ask' it for assets to use.
Just two examples, other could surely be made. The bottom line is that, now that the new API is still fluid, it might be wise to start thinking of ways, protocols, ... by which plug-ins can co-operate and inter-operate.
