Return saving ruleset when mergeWithSaving is true

For the CMS I'm making, I want to get the ruleset for updating/creating, the same as used for the validation (so Former can automatically add html5 rules). But the updating/creating rules aren't always set, sometimes it's just the saving ruleset. When I set the $mergeWithSaving to true, I except this also to be the case when the requested set is empty.
And when they are all empty, I would expect an empty array, to prevent errors with empty foreaches/merges etc.