Two separate questions involved here: employment processing and certification.
As a wild guess, I would suggest that no one will look at an application (except maybe ex-military) if you don't have some multi time. This is a common method of filtering, and possibly an insurance issue?
For an FAA Type Rating, if you don't already have MEL, this is added with the multi-engine type rating. You would however still need to meet the aeronautical experience requirement for the level of certificate (50 hours in class for ATP).