Currently there is only one choose dialog scope so when you implement different workbench and connector you can't really have all different implementations working easily alongside and have them being used from choose dialog. The provider there needs to know about all workbench implementations and they all need to have common ancestor to make it work. this is inflexible and leads to issues where the last one setting the choosedialog scope needs to know about all other impls out there and have dependency on them in order to write provider that is able to work with all those different implementations. See MGNLDAMEXT-13 for example of the problem.