interface inheritance, and especially so in regard to IDisposable

This turns out to be some stupidity on my part. The way out of the problem is to just make an interface inherit from IDisposable, and, yes, you may do that. This suggests that while classes implement interfaces, interfaces do not implement other interfaces they inherit other interfaces, but I wonder if that is true given that an interface may "inherit" more than one interface. Interfaces may not inherit from classes.