Few things that come into my mind:
1. Plugin registration
If you look at the SDK doc/SDK-Tutorial.html there is a section called "Multi vCenters environment" that says the following:
If vSphere Web Client is connected to multiple vCenter servers the plugin UI is only visible for vSphere objects that belong to the vCenters where it is registered. So you should register your solution with all vCenters where you want the solution to be available, it will be installed only once. Of course this doesn't apply to custom objects that are not managed by vCenter.
2. Data retrieval
You should keep in mind that the DataService (depending on your QuerySpec) will return objects from all vCenter Servers.
3. User Experience
You should consider if your views and widgets will display data for all vCenter servers at the same time. This will have performance and scalability implications.
In case you are creating HTML plugin using the HTML bridge you should take a look at /html-bridge/docs/html-bridge.html, section "vCenter Selector". There is also a sample that illustrates how to retrieve data only from one vCenter Server.
You have more specific questions, please let us know :smileyhappy: