There should be some possibility how to share UI among different Debugger Implementations. Sharing of UI should be optional. In runtime, when user defines some instance of Breakpoint On Exception - it will work in both DIs. Add Breakpoint Dialog should be opened with values for it. For example watch displaying value of array can show elements of array as children.
Location can be marked current, can display breakpoint and can be focused - highlighted.
Each invocation of Start Debugging action starts a new debugger session. DIs should be able to share debugger session and to cross among session's languages. Current session can be changed in some Sessions View - visual component containing list of sessions. DIs can share some UI components or create its own.