About the permissions part-
Permissions isnt compatible with everything, the mod/plugin has to work on making it specifically work for permissions. I, as the server manager, would have to find a certain code that lets the user/admin do something.
i.e. worldedit for bukkit- theres like...10000000000 different permissions for it, but I pick and choose what I allow people to do.
Are you sure tekkit supports permissions?
Specifically PermissionsEx