It seems as if removing them would reduce the Mango resource "footprint", i.e. memory and disk space usage. Is this true?

Sure is. But, you'd be talking about not very much memory (since only a few classes from the modules would have ever gotten loaded) and not much disk (I summed up those modules on my machine and for it to be 8.4 MB, so marginal savings there depending on the machine). There would also be a slight but ever-present reduction in bytes transmitted for loading various pages, I would expect.