Why not just move these "skills for passives" to slot 5 and don't touch them anymore?
Or use Srendar to track the abilities of the passive skills in a special list, e.g. bar 7 or 8 which you move to a special place on your UI.
Blocking skills is not possible afaik as you#d need to deactivate the keybind somehow. If this is doable it would be a major problem which should be fixed by ZOs