Or, if I make a mess of new ones, can this function remove them and simply revert to a saved state of hotkeys?
A saved key configuration keeps track of added, removed and modified shortcuts. In fact, it is merely storing differences from (changes made to) default configuration. And when reloaded, it re-creates default keymap, and 'replays' stored modifications over it.
This system also allows to support (relatively) well changes in default keymap, without totally breaking or leaving customized one in frozen, old state.
As far as I know Blender key map editor can currently only add or modify key combination entries, not remove them. I believe I once reported a bug in the tracker about it and one developer told me removing entries was unsupported.
One workaround would be to change the undesirable key mappings to something else, even if non functional, to "disable it" upon impor.